Heidi Alexander has been named the new transport secretary following Louise Haigh's resignation.
The Swindon South MP, who had been serving as a justice minister, previously worked as Sadiq Khan's deputy transport mayor from 2018 to 2021.
Ms Haigh stepped down after Sky News revealed she pleaded guilty in 2013 to an offence involving falsely reporting a work mobile phone as stolen to police.
She claimed the device was stolen when she was "mugged".
In a statement Haigh said she discovered "some time" after the report that the phone had not been taken and was called in for questioning after the device was switched on.
She said the matter was a "genuine mistake" from which she "did not make any gain".
Haigh said: "In 2013 I was mugged while on a night out. I was a young woman and the experience was terrifying. I reported it to the police and gave them a list of what I believed had been taken - including a work mobile phone that had been issued by my employer.
"Some time later I discovered that the mobile in question had not been taken. In the interim I had been issued with another work phone.
"The original work device being switched on triggered police attention and I was asked to come in for questioning. My solicitor advised me not to comment during that interview and I regret following that advice.
"The police referred the matter to the [Crown Prosecution Service] and I appeared before Southwark magistrates. Under the advice of my solicitor I pleaded guilty - despite the fact this was a genuine mistake from which I did not make any gain."
Haigh has been Sheffield Heeley MP since 2015, and became Transport Secretary when Labour won the election in July.
