Transport secretary Louise Haigh has resigned over a conviction she received in 2014 in connection with a mobile phone, which she had wrongly said was stolen.

She had made a mistake but pleaded guilty to making a false report to police, which amounted to fraud by false representation, having been advised by a lawyer not to comment during a police interview.

The case went to Camberwell Green magistrates’ court in London where she was given a conditional discharge, which is technically a conviction but does not involve a fine or other penalty. She was elected as MP for Sheffield Heeley six months later. It is understood that the Prime Minister had been aware of the case when she was appointed transport secretary.

She 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 CPS [Crown Prosecution Service] and I appeared before magistrates' court.’

She has written to Prime Minister Keir Starmer offering her resignation, while assuring him that she remains ‘totally committed to our political project’.

Sir Keir has replied: ‘Thank you for all you have done to deliver this government’s ambitious transport agenda. You have made huge strides to take our rail system back into public ownership through the creation of Great British Railways, investing £1 billion in our vital bus services and lowering costs for motorists. I know you still have a huge contribution to make in the future.’

Ms Haigh is the first cabinet minister to resign since Labour came to power after the General Election on 4 July this year. Her conviction is now spent.

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 judgement to the British public.’ 

One of her priorities had been railway reform, which includes bringing the remaining private sector operators back into public ownership.

Her resignation has come less than 24 hours since it was announced that the Passenger Railway Services (Public Ownership) Act had received Royal Assent.

The new law makes public ownership of railway passenger contracts the default, rather than the last resort.

Ms Haigh had become well known for describing herself as ‘Passenger in chief’, and saying that she intended to ’move fast and fix things’.

The first two private sector passenger operators to be affected by the new Act are set to have their contracts terminated in April.