Neil Parish has told the BBC he is resigning as an MP after admitting he watched pornography twice in Parliament.
Mr Parish, who has represented Tiverton and Honiton in Devon since 2010, said it had been a “moment of madness”.
He said the first time was accidental after looking at a tractor website, but the second time – in the House of Commons – 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, Mr Parish said: “The situation was that funnily enough, it was tractors I was looking at.
“But my crime – biggest crime – is that on another occasion I went in a second time.”
He admitted that second time had been deliberate and that it happened in the House of Commons while he was sitting waiting to vote.
Mr Parish 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.”
He said it was a “moment of madness” but denied watching the material in a way where he hoped other people would see it, saying he was trying to be discreet.
“I was wrong what I was doing, but this idea that I was there watching it, intimidating women, I mean I have 12 years in Parliament and probably got one of the best reputations ever – or did have,” he said.
Asked about why he decided to watch the material in the Commons, Mr Parish said he did not know and that he must have “taken complete leave of my senses” and “sense of decency”.
He 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, adding that he was making a “total full apology” for his actions.