Conservative MP Ross Thomson has announced he is to stand down amid allegations he sexually assaulted a Labour MP in a Westminster bar.

The Aberdeen South MP, who has been in office since 2017, said he made the 'most difficult decision' he could ever make after Glasgow MP Paul Sweeney went public with his allegations this morning.

It is alleged Mr Thomson 'drunkenly' intruded on a conversation Mr Sweeney was having with friends before he pressed his hand down the front of his trousers.

"I felt paralysed. It was just such a shocking thing. I was in a cold sweat, it was mortifying," Mr Sweeney told the Scottish Mail on Sunday. "Nobody knew where to look at the table. It’s embarrassing.

Mr Thomson had released a statement this morning denying any wrongdoing, and has since announced his intention to step down.

READ MORE: Labour MP Paul Sweeney claims he was groped by Tory MP in Commons bar

Writing on Twitter, he said: "I have made clear already today that the allegations printed in the Mail on Sunday are false and defamatory.

"This is a political smear and I will continue to fight to clear my name.

"I will see this investigatory process through to a conclusion.

HeraldScotland: Labour MP Paul Sweeney was among those telling an almost empty house about how much Westminster gives to Scotland

"I always believed politics was about noble pursuits and doing what you believed to be best for your country. My experience is that our politics is now so poisonous that we will never attract good, honest and decent people in the first place.

"I have therefore made the most difficult decision that I could ever make.

"I have decided that I will stand down as the Scottish Conservative and Unionist candidate for Aberdeen South."

Mr Sweeney said he was left feeling 'mortified' after the alleged assault in October last year, and has since branded the investigation by Westminster's standards watchdog a 'shambles'.

But Mr Thomson remains 'confident' the parliamentary standards process will find 'in my favour, and that these baseless claims will be shown up for what they are'.