A top Tory was watching porn on his mobile phone in the House of Commons while sitting alongside a female minister, the Mirror can reveal.
The shocked minister told colleagues about the incident, which happened in the last few months, at a highly-charged meeting of Tory MPs at Westminster last night.
Conservative chief whip Chris Heaton-Harris is investigating the shocking reports, his office has said.
A statement from the whips office said: "The chief whip is looking into this matter. This behaviour is wholly unacceptable and action will be taken.''
Two of those present claimed she had described the suspect as a "frontbencher" - a minister or a whip - but a third witness said she had only mentioned a Tory "MP". A source in the whips office claimed it was a backbencher.
Three sources said that around a dozen women MPs at the meeting shared accounts of alleged sexism and harassment by their colleagues.
One MP recounted how a female colleague in a knee-length leather skirt had been told by a male MP: "That's a nice outfit. What do you do for your day job?".
Another claimed that a Tory whip had ushered women MPs into the voting lobbies in recent weeks, by instructing: "Come on, girls!"
The new Tory sexism storm comes after reports that 56 MPs, including three Cabinet ministers, are facing allegations of sexual misconduct after being reported to Parliament's Independent Complaints and Grievance scheme.
It also follows a sexism row in which Labour deputy leader Angela Rayner was accused of 'Basic Instinct' ploy to distract Boris Johnson at Prime Minister's Questions.
The meeting of between 40 and 50 Tory MPs, known as the 2022 group, was attended by new chief whip Chris Heaton-Harris, Tory party chair Oliver Dowden and Commons leader Mark Spencer.
Some male colleagues also attended, including one former minister who sources said asked the party bosses whether any Tory MPs found guilty by the Parliamentary probe would be kicked out of the party.
Several women MPs raised concerns that the toxic atmosphere within the party could put women off standing for Parliament.
Sources in the room said that former PM Theresa May, who was present for some of the MPs' testimony, looked on “with a face like thunder”.
One MP said: “It was like a blood-letting. Everybody was sharing awful stories of what had happened to them in the Commons at the hands of male MPs.
"[The chief whip] clearly hadn’t been expecting it and looked knocked for six. But the big question is what happens next”.
Another added: "They were genuinely shocked and horrified. They must realise that there are serious issues they need to address".
Boris Johnson was grilled at Prime Minister's Questions on whether sexual misconduct would be "grounds for dismissal" for ministers following the reports that a string of senior MPs are under investigation.
Green Party MP Caroline Lucas said: "The Prime Minister has just rightly said that there can be no place for sexism and misogyny in this House, so can he now confirm whether he considers that sexual harassment, apparently unlike bullying and lying, is grounds for dismissal under the ministerial code?"
Mr Johnson replied: "Of course sexual harassment is intolerable and it is quite right that members should now have a procedure by which they can bring that to the attention of the House authorities and I think that is a good thing, and of course it is grounds for dismissal."
Tory MP Pauline Latham told GB News the MP in question “should go - that will mean their ministerial career is absolutely shot and their parliamentary career probably.
“It’s just not excusable in any way. It’s totally shocking.”
Mr Johnson's press secretary insisted that the Tories did not have a problem with misogyny and sexism.
She said: "You will have heard the PM address this explicitly in Parliament today and over the last few days, saying there is absolutely no place for such behaviour and this cannot be tolerated in any workplace."
Asked whether watching pornography at work was a sackable offence, she said: "I am not aware of the disciplinary action.
"Obviously, it is wholly unacceptable behaviour and it is being looked into."
