Reeves put her four-bedroom south London home up for rent in July 2024, when Labour won the general election and she moved into 11 Downing Street.

The house falls in an area where Southwark Council requires private landlords to obtain a selective licence at a cost of £945. Reeves or her letting agent could face an unlimited fine if the council takes the matter to court.

Southwark Council has refused to comment on Reeves’s case but said it only takes enforcement action against landlords who do not apply for a licence within 21 days of receiving a warning or where a property is found to be in an unsafe condition.

Reeves says she has now applied for a licence.

The chancellor said she first became aware that her property did not have the correct licence on Wednesday when the Daily Mail, who first reported the story, contacted her.

After reviewing the emails between the estate agent and Reeves’s husband, the prime minister’s ethics adviser Sir Laurie Magnus said on Thursday night that he “remains of the view that this was an unfortunate but inadvertent error”.

While he did not rule on whether the ministerial code had been broken, Sir Laurie said he found “no evidence of bad faith”.

In a letter to Reeves on Thursday evening, Sir Keir said he agreed with his ethics adviser and saw “no need for any further action”.

He accepted the emails from the estate agent were only found by her husband on Thursday morning and Reeves was “acting in good faith”.

However, he added: “It would clearly have been better if you and your husband had conducted a full trawl through all email correspondence with the estate agency before writing to me yesterday.”

Defending his colleague, Trade Minister Chris Bryant said he did not think the fault lay with Reeves and she would be “entitled to feel a bit grumpy” about the situation.

“She realised that her husband had actually had some emails, some correspondence with the estate agent – and the estate agent had said categorically in terms we will sort out this licence for you and then subsequently it didn’t happen,” he told the BBC.

The revelations come at a politically awkward time for Reeves, who is preparing for a Budget at the end of the month amidst speculation the government is planning to break a manifesto commitment not to raise income tax.