The Conservative MP being investigated for allegedly watching pornography in the Commons chamber is expected to give into pressure to resign despite arguing he opened the material accidentally as he fought to stay in power.

Neil Parish will “likely” quit as the representative for Tiverton and Honiton on Saturday, a Tory source told the PA news agency, stressing that nothing is confirmed.

A second Conservative source, in the Devon constituency, suggested Mr Parish was bowing to pressure from Westminster while local Tory officers were saddened by the scandal.

The select committee chair had initially vowed to continue working as an MP after he was suspended from the parliamentary Conservative Party when he was revealed to be the man at the centre of the allegations.

Sky News, which first reported the possible development, suggested Mr Parish had been told by allies his position had become untenable.

They are said to have voiced concerns about the way he maintained his silence as rumours swirled about who the culprit was since two Tory MPs aired the accusations on Tuesday.

The backbencher had been pledging to continue his “duties” as the MP for the Devon constituency and as chairman of the Commons Environment, Food and Rural Affairs Committee.

Asked by reporters at his Somerset farmhouse if he opened something in error in the Commons, he said: “I did, but let the inquiry look at that.”

However, there have been suggestions that a Tory minister also witnessed him watching porn on a second occasion, in a committee meeting.

In an interview later conducted in his dressing gown on Friday night, Mr Parish told the Telegraph how “it’s almost as if a weight is lifted off me” now the accusation is “out in the open”.

Mr Parish referred himself to Parliamentary Commissioner for Standards Kathryn Stone for investigation, but said on Friday he would only resign if she found him guilty.

Senior Tory Karen Bradley had urged him to stay away from Parliament and Harriet Harman, the longest-standing female MP, called for his immediate resignation.

On Saturday morning, safeguarding minister Rachel Maclean backed the 65-year-old farmer’s decision not to immediately stand down, saying: “I genuinely think that’s a matter for him.”

But, speaking to Times Radio, she added: “I want to be clear, he is not continuing his business as normal, he’s under investigation, and I’m confident that the appropriate measures will be put in place to safeguard any of his constituents, particularly women and girls.”

Ms Maclean, the minister responsible for safeguarding women, said “clearly what he’s done is unacceptable” and that he should resign if found to have watched the material deliberately.

Senior Conservative Caroline Nokes, who chairs the Women and Equalities Committee, said it would be “difficult” for Mr Parish to spend the required time in Parliament as a select committee chair.

She also accused the Tory whips of “dither and delay” in not suspending the MP from the parliamentary party until Friday, despite colleagues airing the claims in a meeting three days earlier.

However, she suggested it will be a challenge for Mr Parish, who has been an MP since 2010, to continue leading his committee examining environmental matters.

“It’s a senior and responsible position and as a select committee chair myself I know how seriously I take that job,” she told BBC Radio 4’s Today programme.

“That’s a matter for Neil to discuss with the party whips and to take a position on, but I think whilst he’s under investigation it’s going to make it very difficult for him to be in the Commons as much as he needs to be.”

Mr Parish referred himself for investigation by the Commons sleaze watchdog after a conversation with Chief Whip Chris Heaton-Harris on Friday.

Separately, the Independent Complaints and Grievance Scheme (ICGS), which looks into claims of bullying and sexual harassment, is understood to have begun examining events after at least one witness made a referral.

Mr Parish had said in a statement on his website he “will be co-operating fully with any investigation, and whilst it is ongoing I will continue to perform my duties”.

Ms Bradley, who chairs the Procedure Committee, said she “would urge him not to come into Parliament” while under investigation and was clear he must quit if found guilty.

“I’m struggling to find an excuse, I’m struggling to find a reason that might mean it was acceptable, but let’s let the investigation take its course,” she told Channel 4 News.

Labour’s Ms Harman called on Mr Parish to stand down amid a “new low for the House of Commons”.

She told BBC Radio 4’s PM programme: “If this is what he has done, he should stand down from Parliament right away. It is not right for him to go through the investigation processes if that is what he has done.

“Clearly he is not fit to be in Parliament. He should accept that and not drag the processes out.”

Liberal Democrat deputy leader Daisy Cooper called on Prime Minister Boris Johnson to order Mr Parish to “resign immediately”.