Gordon Brown twists the knife as he slams Keir Starmer for being 'too slow' on Mandelson and warns Labour: 'Clean up or pay heavy price'

Among the accusations are that Lord Mandelson leaked market-sensitive No10 documents to Epstein during the 2008 financial crisis, while serving as Buisness Secretary in Mr Brown’s cabinet.

On Friday night, police raided Lord Mandelson’s homes in Camden and Wiltshire as part of an inquiry into alleged misconduct in public office.

Mr Brown admitted he regretted appointing Lord Mandelson in 2008, describing the alleged leaking of commercially sensitive material as “a betrayal of everything we stand for as a country” and “a financial crime”.

He said: “I have to take personal responsibility for appointing Mandelson to his ministerial role in 2008. I greatly regret this appointment.”

While insisting Sir Keir is “a man of integrity” who “wants to do the right things”, Mr Brown suggested he had acted too slowly in the matter.

“Perhaps he’s been too slow to do the right thing. But he must do the right things now,” he said, urging the Prime Minister to act decisively.

Mr Brown did provide some comfort for the embattled Sir Keir, defending his decision to appoint Lord Mandelson as ambassador to Washington.

“Keir Starmer was misled, and he was betrayed.

“There is a systematic failure to do proper vetting,” he wrote in The Guardian, demanding sweeping reforms.

The former Prime Minister called for an anti-corruption tsar and a ban on most second jobs for MPs, warning: “There has been a system failure and we’ve got to rectify it.”

The Metropolitan Police formally launched its criminal investigation into allegations about Lord Mandelson on February 3.

On Friday, officers were spotted outside his £7.6million Regent's Park property.

A second search took place at another property connected to Lord Mandelson in Wiltshire.

On Saturday morning, Scotland Yard confirmed its investigation into Lord Mandelson will be “complex” and require “a significant amount of further evidence gathering and analysis” following the raids.

Deputy Assistant Commissioner Hayley Sewart, of the Metropolitan Police, said: “I can confirm that officers from the Met’s Central Specialist Crime team have carried out searches at two addresses, one in the Wiltshire area, and another in the Camden area.

"The searches were related to an ongoing investigation into misconduct in public office offences, involving a 72-year-old man.

“He has not been arrested, and enquiries are ongoing. This will be a complex investigation requiring a significant amount of further evidence gathering and analysis.

"It will take some time to do this work comprehensively, and we will not be providing a running commentary.”

Sir Keir, who accused his one-time ally of being a "liar" and accusing him of "betrayal" earlier this week, is under increasing pressure after appointing Lord Mandelson as the UK's Ambassador to the US.

He was forced to sack the peer from the role in September last year following fresh revelations about Lord Mandelson's relationship with Epstein.

Speaking in Hastings on Thursday, the Prime Minister said: “The victims of Epstein have lived with trauma that most of us could barely comprehend, and they have to relive it again and again.

"They have seen accountability delayed and too often denied to them.

“I want to say this. I am sorry–sorry for what was done to you, sorry that so many people with power failed, sorry for having believed Mandelson’s lies and appointed him, and sorry that even now you’re forced to watch this story unfold in public once again.”

Lord Mandelson has previously denied any wrongdoing in relation to Jeffrey Epstein.

He stated: "I was never culpable or complicit in his crime. Like everyone else, I learned the actual truth about him after his death."

The peer said he had "relied on assurances of his innocence that turned out later to be horrendously false".

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