Labour MP Clive Lewis has been accused of groping a woman at the party's annual conference.
The Norwich South MP "completely" denied the allegation, which is being investigated by party officials.
A formal complaint was lodged against Mr Lewis on Friday.
He is said to have hugged the woman and given her backside "a big squeeze" at the event in Brighton in the summer, according to a report in the Independent.
Mr Lewis denied the accusation shortly after, saying "it's not what I do".
The 46-year-old is the latest MP to be accused of inappropriate behaviour as Westminster is swamped with similar allegations.
Pouring scorn on the accusation, he said many MPs were "sat there thinking: 'Whose turn is it next?'"
"I don't as a rule at packed Labour party conferences grope people's bottoms when I greet them. It's just not how I roll, it's not what I do," he said.
"Is the person mistaken? Have I given them a hug and this has been misinterpreted? I don't know.
"All I know is that I would not deliberately do that, do what's alleged. I completely deny that.
"I'm feeling pretty taken aback by it all. It's not been a great week ... for Parliament. It's been a pretty tough fortnight."
A Labour party spokeswoman said: "The Labour Party is investigating a formal complaint made today against Clive Lewis."
Mr Lewis faced criticism last month after a video emerged, reportedly from the same conference event, telling a man to "get on your knees bitch"