Sir Keir Starmer's principal private secretary, Ninjeri Pandit, is leaving her job assisting the Prime Minister after less than a year in the role.
The Prime Minister had "become concerned" that Ms Pandit was "ineffective" in the role, the BBC reports.
A Downing Street source insisted that the aide retained Mr Starmer's "trust and confidence".
She is the third senior aide to the Prime Minister to leave their role in 12 months, after chief of staff Sue Gray and director of communications Matt Doyle.
While Ms Doyle and Mr Gray were political appointees, Ms Pandit is a civil servant.
It is expected that Ms Pandit will move to another role in the Government.
Before becoming Mr Starmers' principal private secretary, Ms Pandit ran the No10 policy unit during Rishi Sunak's premiership and was chief of staff to the chief executive of NHS England earlier in her career.
After a series of rebellions from backbenchers in the Labour Party before the summer break, many in the Government are expecting Sir Keir to soon begin a reshuffle of his junior ministers as his premiership faces a growing threat.
No10 declined to comment when approached by GB News.
FOLLOW BELOW FOR LIVE UPDATES THROUGHOUT THE DAY…
Giving illegal migrants 'temporary legal status' is a 'very good idea', Ed Davey tells GB News
Sir Ed Davey has demanded an 'apology' from Nigel Farage and the Conservatives
|GB NEWS
Sir Ed Davey told GB News that giving illegal migrants "temporary legal status" is a "very good idea".
Speaking on GBN Breakfast, the Liberal Democrat leader said: "Liberal Democrats have long argued that people waiting months and months for asylum applications, having to be housed in hotels at great expense to the taxpayer, should actually be asked to work, and therefore, rather than costing us, they can actually contribute to our economy and to the Exchequer.
"It seems a sensible approach, and Liberal Democrats have long argued that these asylum hotels are a sign of the mistakes of the Conservatives.
"First of all, they failed to process asylum applications quickly enough. They deliberately created this backlog, which led to the hotels in the first place.
"The hotels are the conservatives' fault and then if we're going to now solve that and prevent that mistake from going on and costing us all a fortune, I think things like not just processing the applications more quickly, but getting people to actually work and contribute."
'There is no silver bullet here!' Labour MP Stephen Morgan GRILLED over Labour’s illegal immigration policy
Labour MP Stephen Morgan claims "there is no silver bullet" to Labour’s illegal immigration crisis.
Rachel Reeves 'to squeeze £2BILLION from landlords' in fresh tax raid on 'unearned income'
Allies of Rachel Reeves have argued slapping property owners with a fresh tax would not break her 'red lines'
|GETTY
Rachel Reeves is considering a major new tax raid on landlords' "unearned" income in a bid to raise as much as £2billion.
Treasury officials are said to be looking into how to levy National Insurance on rental income with just weeks remaining until the Chancellor's second autumn Budget.
At present, NI does not have to be paid on most earnings from pensions, property, and savings.
State pension age should be 'pushed back' to 75 under 'radical reset', Labour told
The Labour Government should raise the state pension age to 75 years old to ensure the retirement system does not collapse in the years to come, according to a leading economist.
Tom McPhail, the host of the Pensions Monkey podcast, has suggested radical reform is needed to make sure the retirement benefit remains financially viable in the long-term.
His intervention comes after the Office for Budget Responsibility (OBR) signalled the triple lock has become an unaffordable expense for the British taxpayer to keep paying.
Tony Blair attends White House meeting and advises Donald Trump on future of Gaza
Tony Blair has travelled to Washington DC to discuss a plan to rebuild Gaza with Donald Trump, a White House official has revealed.
The former British Prime Minister met with the US President on Wednesday as tensions in the Middle East rose following a strike on the city, which killed 20 people, including journalists and hospital workers.
The Potus has previously suggested Palestinians should be dispersed to neighbouring countries, with the US taking control of the strip of land.
He described the controversial suggestion as “the Riviera of the Middle East.”, but it appears the President has backed away from this idea.
Katherine Forster breaks down what Brexit meant for illegal migration
GB News Political Correspondent Katherine Forster breaks down what Brexit meant for illegal migration.
Speaking on GB News, she said: "We know that Ed Davey is very anti-Brexit, very keen for us to go back in the single market, making Nigel Farage responsible for some of the small boats crisis.
"Certainly, Brexit did make it more difficult in that we don't have that agreement under the Dublin Convention, but the reality is that under the whole of the European Union, you're supposed to go back to the country that you first landed in to claim asylum. Practically speaking, it isn't working in the EU and hasn't worked in the EU for ages."
She highlighted that the leader of the Liberal Democrats has consistently taken a very tough line on Trump, despite opposition political parties changing their views.
Katherine added: "Ed Davey has, from the very beginning, been very tough on Trump. As much as you can say that Donald Trump really isn't going to care if Ed Davey is not at the banquet and probably isn't going to notice, I think that's true. This is about sending a message, as he said, this is about Ed Davey coming on TV making news with this announcement, because although the Lib Dems have got 72 MPs, they really struggle to be heard.
"Reform has got four [MPs] and we've spent a couple of days talking about everything that Nigel Farage is proposing if Reform gets into Government.
"I think the Lib Dems will be happy with this announcement. They don't want to upset the King, but they think that this is necessary.
"I suspect where they are right is where he says that Donald Trump has the power to influence Netanyahu and make a difference with this. Because really, no matter what all these other countries say, no matter what Keir Starmer says, no matter that he's threatening to recognise Palestine as a state. Benjamin Netanyahu is really interested in what our Prime Minister says, or lots of other leaders. But Donald Trump and the US, that is a different matter."
Sir Ed Davey demands Nigel Farage and the Tories apologise for Brexit
Liberal Democrat leader Sir Ed Davey demands Farage and the Tories apologise for Brexit.
He told GB News: "The truth is, the small boats are a sign of policy failure."
Mr Davey blamed both the Conservatives and Nigel Farage for the migrant crisis.
He added: "Before Brexit, we had a returns agreement with every European country, which meant we could, through the Dublin Convention, automatically return people on small boats. We don't have that legal power anymore and the French and others have made it very difficult for us to return these people in the small boats.
"It's got far, far worse. We didn't have this problem before Brexit. So I think Nigel Farage has been very vocal, hasn't he, over the summer.
"We should start with an apology, and the Conservatives should apologise. They cause this problem. They have wasted billions of pounds, and all these people are protesting.
"They should be protesting at Nigel Farage and the Conservatives, who cause this chaos."
Ed Davey tells GB News he plans to boycott Donald Trump state dinner
Liberal Democrat leader has said he will not attend a state dinner with Donald Trump in protest over the humanitarian crisis in Gaza.
Sir Ed Davey told GB News: "Over the summer, we've seen the devastation and Humanitarian crisis in Gaza reach new lows. We've seen children starving. We've seen the lifeless bodies of many children. We've seen a famine officially declared in Gaza City, and we've seen the emaciated bodies of the hostages that Hamas outrageously took.
"This has to end. We need the ceasefire. We need the hostages out and we need the aid in. There is one man who has the power to do that, and that's Donald Trump. He could pick up the phone today. Talk to Netanyahu, the Prime Minister of Israel, and get him to act and do the right thing. He could also pick up the phone to the Qatari government and the Gulf states, and get them to put pressure on Hamas to release the hostages.
"What I wanted to do by this decision, which, as I say, was very difficult, was to highlight the fact that Donald Trump coming to our country is the one man who can bring an end to all this and our media, the Government and frankly, the British public need to make that clear to Donald Trump. He has to act to end this humanitarian crisis."
The Liberal Democrat leader accused the Conservatives of failing to "stand up to Donald Trump and called out Netanyahu over what's happening in Gaza."
He added: "Anyone who's looked at the situation in the Middle East over many years knows it's the US President who has huge power. Even more so at the moment, actually, the Netanyahu Government is facing a backlash amongst many Israelis who think its strategy threatens the lives of the hostages. So I think there is a real chance for the President of the United States to do the right thing.
"I'm afraid that when I've listened to Donald Trump talking about this and talking about Gaza as a great real estate opportunity, it looks like the reverse. He sometimes says he regrets the killings. He does nothing about it. I've always been pro-American. I see the US as our strongest ally. I believe in talking to people, including Donald Trump. But my chance as the leader of the Liberal Democrats at this moment is to send this message by not going to the banquet."
Epping migrant hotel fresh legal battle to begin TODAY as court prepares for Labour appeal
The Epping migrant hotel legal battle will restart tomorrow | GETTYThe Epping migrant hotel legal battle will restart today as the court prepares for a Labour appeal of the decision to remove asylum seekers from the accommodation.
The owner of The Bell Hotel in Epping will also challenge the decision at the Court of Appeal today.
Epping Forest District Council was successful in their bid for an interim injunction to stop migrants from being housed at the Bell Hotel earlier this month.
Currently, the hotel must stop housing the asylum seekers by September 12.