WELSH Secretary Alan Cairns has quit the UK Government over allegations he knew about an aide’s sabotage of a rape trial.

The shock resignation comes on the first day of campaigning for next month's election.

It’s the first time a minister has resigned in shame during a campaign since 1975.

The row dates back to a 2018 court case when Cairns’s staff member, Ross England, made claims about a rape victim's sexual history, leading to the collapse of trial.

READ MORE: Tory minister told of candidate's rape trial 'sabotage' before selection

Cairns denied knowing about this, saying he only became aware of his aide’s role in the trial's collapse when the story broke last week, but leaked emails suggest he was told about the case in August 2018.

England was then picked as a Tory candidate for the Welsh Assembly in December 2018, thanks in part to Cairns’s endorsement.

The minister praised him as a "friend and colleague" with whom "it will be a pleasure to campaign".

During the trial of his friend James Hackett, England told the court he had a casual sexual relationship with the complainant – which she denied.

This was despite the judge making it clear that evidence of the sexual history of the victim was inadmissible.

The judge, Stephen John Hopkins QC, said to him: "Why did you say that? Are you completely stupid?

"You have managed single-handed, and I have no doubt it was deliberate on your part, to sabotage this trial … get out of my court."

Hackett was convicted of rape at a retrial.

Asked if the minister should resign, the victim – who worked for the Tories – told the BBC: "Absolutely. If he'd come out and condemned Ross [England] in the first instance, he wouldn't be in this position.

In his resignation letter, Cairns promised to "cooperate in full with the investigation under the Ministerial Code which will now take place".

He says he is confident he will be "cleared of any breach or wrongdoing".

The Tories have not had the best start to their election campaign.

Jacob Rees-Mogg, the leader of the House of Commons has been forced to apologise for claiming the victims of the Grenfell Tower fire didn’t have “common sense”.

READ MORE: Jacob Rees-Mogg says sorry over Grenfell tower comments

The party has also been accused of lying after releasing a doctored video of Labour’s Keir Starmer looking stumped at a journalist’s question about Brexit.