Rachel Reeves was warned twice about needing a letting licence for renting out her £3,200 a month home despite telling the Prime Minister she was unaware.
The Chancellor admitted to breaking housing rules after she rented out her family home in Dulwich without a licence.
Ms Reeves initially claimed she and her husband were unaware about the licencing requirements, and instead blamed Harvey & Wheeler, the lettings agency used.
Emails then emerged which showed the Chancellor's civil servant husband, Nicholas Joicey, had in fact been informed about the licence.
Now, a source has said that Ms Reeves and her husband had originally contacted the estate agency Knight Frank about managing the property.
At that point, Knight Frank warned them about the need for a licence, according to the Mail on Sunday.
A spokesman for the agency said on Saturday: "It is standard procedure to notify all clients of their legal and regulatory obligations when letting a property."
Sir Keir Starmer berated Ms Reeves for the original miscommunication regarding the email chain with Harvey & Wheeler, however he insisted there was no need for further action.
Rachel Reeves admitted breaking housing rules after she rented out her family home in Dulwich without a licence
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However, the new revelation has sparked fury among the Conservatives as senior members argue it shows Ms Reeves was warned about the licence on two separate occasions by two different estate agents.
Shadow Treasure Minister, Gareth Davies, said: "Each day brings fresh questions about Rachel Reeves' account.
"This latest revelation casts serious doubt on her claim not to have known about the need for a licence. Her story seems to shift with every explanation.
"The Prime Minister must now get to the bottom of this and order a full investigation without delay."
RACHEL REEVES'S RENT ROW - READ MORE:
Sir Keir Starmer berated Rachel Reeves for the original miscommunication
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It is not known why Knight Frank did not end up being used to manage the property on behalf of the Chancellor and her husband.
The firm said the lack of licence was not the reason.
The Prime Minister's Independent Adviser on Ministerial Standards Sir Laurie Magnus said he believed Ms Reeves made an "unfortunate but inadvertent error".
He added that she "assured me of her confidence that all relevant facts have been disclosed".
The Chancellor placed her family home in south London (pictured) on the rental market for £3,200 a month last year
| RIGHTMOVEReferencing the email chain with Harvey & Wheeler which at first was not mentioned, Sir Laurie said it was "clear" that Mr Joicey did not remember the exchange "which took place at a very busy time".
Although he called the mixed messages "regrettable", the Independent Adviser said there was "no evidence of bad faith" from Ms Reeves.
The Chancellor has conceded it was her responsibility to obtain the licence, and has since taken measures to do so.
When asked about the revelation regarding Knight Frank, Ms Reeves' spokesman said: "You have the conclusion of Laurie Magnus, and the exchange of letters from October 30 where Rachel Reeves references correspondence from Harvey & Wheeler that says a Selective Licence would be required."