New Transport Secretary announced after Louise Haigh's resignation over conviction

She said in a letter to Sir Keir Starmer that the matter would have been a “distraction” from her work delivering Government policy.

Swindon South MP Ms Alexander had been made a justice minister after Labour won the election in July.

Ms Haigh said that she was mugged in London and gave police a list of stolen possessions, including a work phone, when she reported the incident.

She said she later found the phone was still in her house.

In a letter to Sir Keir Starmer she said: “I should have immediately informed my employer and not doing so straight away was a mistake.

“I appreciate that whatever the facts of the matter, this issue will inevitably be a distraction from delivering on the work of this government and the policies to which we are both committed.”

It is understood the incident was disclosed to Sir Keir when she joined the shadow cabinet.

Ms Haigh pleaded guilty in court over the incident on the advice of a solicitor and magistrates gave her the “lowest possible outcome”, she said in a statement.

It is understood that it was a fraud offence and that the conviction is now spent.

On Thursday evening, Sky News and the Times newspaper reported that Ms Haigh had admitted an offence in 2014 following the incident.

Ms Haigh’s employer at the time launched an investigation after she said that company mobile phones had been stolen or had gone missing on repeated occasions, the Times reported.

She was working for insurance giant Aviva at the time of the incident, according to the reports.

Ms Haigh has been Sheffield Heeley MP since 2015 and held a number of shadow ministerial and shadow cabinet roles before becoming Transport Secretary when Labour won the election in July. Before she entered politics she spent time as a special constable.

Sir Keir said in his reply to Ms Haigh that she had made “huge strides” as Transport Secretary to take the rail system back into public ownership through the creation of Great British Railways and investing £1 billion into vital bus services.

“I know you still have a huge contribution to make in the future,” he added.

A Conservative Party spokesman said: “Louise Haigh has done the right thing in resigning. It is clear she has failed to behave to the standards expected of an MP.

“In her resignation letter, she states that Keir Starmer was already aware of the fraud conviction, which raises questions as to why the Prime Minister appointed Ms Haigh to Cabinet with responsibility for a £30 billion budget?

“The onus is now on Keir Starmer to explain this obvious failure of judgment to the British public.”