LONDON - Britain's transport minister Louise Haigh has resigned after pleading guilty years ago to an offense in connection with misleading police over a work mobile phone, in another blow to Prime Minister Keir Starmer.

Her resignation, the first from Starmer's top team of ministers since winning a landslide election victory in July, came after media reports that she had been convicted and given a conditional discharge in 2014 for what she described as a "mistake".

Haigh said in a letter to Starmer dated Thursday, Nov 28, that she had told police she had lost a mobile phone during a "terrifying" mugging on a night out in 2013, only to discover later that the phone was still at her home.

In her resignation letter shared by Starmer's office early on Friday, Haigh said she was standing down as the issue "will inevitably be a distraction from delivering on the work of this government and the policies to which we are committed".

"I remain totally committed to our political project, but I now believe it will be best served by my supporting you from outside government," she said.

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Starmer thanked Haigh for her work and for all she had done "to deliver this government's ambitious transport agenda".

The opposition Conservative Party said Haigh had "done the right thing" but asked why Starmer had appointed her when he was apparently aware of her fraud conviction.

"The onus is now on Keir Starmer to explain this obvious failure of judgment to the British public," a spokesperson for the Conservative Party said in a statement.

Haigh's resignation is yet another blow to the Labour leader, who has seen his party's approval ratings plunge since July.

Almost immediately after winning power, the Labour government came under fire for limiting fuel payments to the elderly and for taking donations for clothing and hospitality.

Since then, his government has angered farmers over changes to inheritance tax rules, and many businesses have cried foul over Labour's first budget in which the finance minister raised taxes mainly on firms and the wealthy.

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Haigh, who was first elected in 2015 and has held senior posts under both Starmer and left-wing former Labour leader Jeremy Corbyn, said the incident with the phone was a "genuine mistake" from which she "did not make any gain".