Welsh Secretary Alun Cairns has resigned after being accused of "brazenly lying" about his knowledge of an allegation that a Tory candidate had sabotaged a rape trial.

The Cabinet minister's decision to quit will rock the Conservative Party which is officially launching its election campaign on Wednesday.

In a letter to Prime Minister Boris Johnson, Mr Cairns said: "You will be aware of allegations relating to the actions of a Party employee and candidate for the Welsh Assembly elections in the Vale of Glamorgan.

"This is a very sensitive matter, and in light of continued speculation, I write to tender my resignation as Secretary of State for Wales.

"I will cooperate in full with the investigation under the Ministerial Code which will now take place and I am confident I will be cleared of any breach or wrong doing."

Mr Cairns claims he had been unaware of former staff member Ross England's role in the collapsed trial until after the story broke last week.

But BBC Wales said it had obtained a leaked email sent to Mr Cairns which showed he had been made aware of the allegations as early as August last year.

Mr England was suspended as a candidate and as an employee last week after details of the court case emerged and the party said a "full investigation will be conducted".

Preseli Pembrokeshire AM Paul Davies, leader of the Welsh Conservatives, said: “I am sorry to see Alun resign today as the Secretary of State for Wales however, under the circumstances this was the right decision for him. Alun has rightly stated that he will cooperate fully with any investigations.

“I would like to thank Alun for his service to Wales as our Secretary of State where he brought an end to the Severn Bridge Tolls which will leave a lasting legacy on the Welsh economy.”