Neil Parish has told the BBC he is resigning as an MP after admitting he watched pornography twice in the House of Commons.
Mr Parish – the MP for Tiverton and Honiton in Devon – said it had been a “moment of madness” and “I was not proud of what I was doing.”
He said the first time was accidental after looking at a tractor website, but the second time was deliberate.
He was suspended by the Conservative Party on Friday over the allegations.
Two female colleagues claimed they had seen him looking at adult content on his phone while sitting near them.
In an exclusive interview with BBC South West, he said: “The situation was that – funnily enough it was tractors I was looking at. I did get into another website that had a very similar name and I watched it for a bit which I shouldn’t have done.
“But my crime – biggest crime – is that on another occasion I went in a second time.”
Asked if that was deliberate, he replied: “That was deliberate… that was sitting waiting to vote on the side of the chamber.”
He said what he did “was absolutely totally wrong”, adding: “I will have to live with this for the rest of my life. I made a huge terrible mistake and I’m here to tell the world.”
Mr Parish appeared emotional as he said he was standing down after seeing the furore and damage it was causing his family, his constituency and local association.
“I was wrong, I was stupid, I lost sense of mind,” he said.
But he denied watching the material in a way where he hoped other people would see it.
He told the BBC: “I make a full apology. A total full apology. It was not my intention to intimidate.”
Neil Parish said last night that he would remain an MP while his conduct was investigated.
But overnight, under significant pressure, he has changed his mind.
This will trigger a by-election in what is a safe Tory seat.
But the bigger picture here matters too. Westminster has been rocked by allegations of a sexist culture this week. If Mr Parish had continued as an MP, he would have been plagued by questions over his conduct.
Caroline Nokes questioned this morning whether he would be able to do his job as extensively as required. Others suggested it would be impossible for him to continue to hold his influential position chairing the environment committee.
This story – and others – have damaged Parliament’s reputation. They’ve also damaged the Conservative Party. Both will be hoping that Mr Parish’s resignation will help them start to move on.
Mr Parish’s local party, Tiverton and Honiton Conservatives, said it supported his decision to step down.
“We would like to take this opportunity to thank Neil Parish for his service to our communities over the past 12 years,” it added.
In an earlier interview with the Times, Mr Parish’s wife, Sue Parish, said the allegation was “very embarrassing” and described her husband as “quite a normal guy” and “a lovely person”.
“If you were mad with every man who looked at pornography, you would not have many wives in the world,” she said.
She added she did not see the attraction of pornography.