A formal investigation has been launched by Labour after a woman accused Clive Lewis of groping her at the party’s annual conference in Brighton.

The 39-year-old woman has alleged that Mr Lewis, a former frontbencher and ally of Jeremy Corbyn, had given her backside a “big squeeze” when he had hugged her in a packed room.

The woman has now made an official complaint and the party has confirmed that it is investigating but Mr Lewis has vehemently denied the allegation.

The woman claimed the incident took place at the same event at which Mr Lewis was recorded saying “get on your knees, b****”, a remark he has apologised for.

She claimed that she had introduced herself to Mr Lewis at the Momentum-organised World Transformed event which ran parallel to the official conference.

She told the Independent: “We had a hug and while we were having a hug he gave my bum a big squeeze.

“My friend who was there, a fellow [constituency party] delegate…me and him looked at each other and our eyebrows went ‘whoaaa’.”

She added: “You kind of jump. I didn’t feel grossed out. I definitely laughed. It felt like if you are hugging a mate. I don’t know. It was over familiar. I had never met him before.”