Boris Johnson has dodged questions about whether he attended a Downing Street drinks party during the first coronavirus lockdown.

The Prime Minister refused to say whether he and his wife, Carrie, attended the gathering in May 2020 allegedly organised by his principal private secretary Martin Reynolds.

Mr Johnson insisted it was a matter for Sue Gray, the senior official leading an investigation into reports of lockdown-busting parties across Whitehall.

The Sunday Times alleged that the Prime Minister attended the event in the No 10 garden with Mrs Johnson on May 20.

The newspaper cited three sources who said Mr Reynolds emailed officials with an invite, adding “BYOB”, meaning “bring your own bottle”.

Asked if he attended, the Prime Minister told reporters: “All that, as you know, is the subject of a proper investigation by Sue Gray.”

Pressed on whether he had been interviewed by Ms Gray, he said: “All that is a subject for investigation by Sue Gray.”

Downing Street denied reports that Mr Reynolds is to be moved to another post following the claims.

The Prime Minister’s official spokesman said he was staying in his current role.

“The Prime Minister has full confidence in his team. There is no change in that post,” he said.

The spokesman also refused to be drawn on reports that Mr Johnson had attended the event.

“There is an independent process going on to look into this, led by Sue Gray, and I can’t comment further while that is taking place.”

Labour leader Sir Keir Starmer said the Prime Minister would have “very serious questions to answer” if Ms Gray found he had attended one of the parties under investigation.

Asked whether Mr Johnson would have to resign, Sir Keir said: “We need to let the inquiry take its course, see what the findings are.

“The Prime Minister has insisted he broke no rules, so if the finding is that he did then he will obviously have very serious questions to answer.”