Owen Paterson MP has said a vote of no-confidence in the Prime Minister was triggered because all the "monkeying around" was "making people really angry".
The Conservative politcian submitted his letter to 1922 Committee chairman, Sir Graham Brady, last night, leading to speculation that his was the 48th letter that triggered the vote.
"We want to deliver what the people voted for. There will be mass disillusion if we don't deliver that," he told talkRADIO's Julia Hartley-Brewer.
- Read more: Vote of no-confidence in Theresa May triggered after 48 letters received
- Read more: Ann Widdecombe: Theresa May's Brexit deal is a 'surrender' to the EU
"We have a manifesto commitment to it, as do Labour actually, and all this monkeying around we've had is making people really angry."
The politician said he thought "long and hard" about submitting his letter, but claimed he had simply "lost confidence" in the Prime Minister's ability to see Brexit through.
"I've thought long and hard about this, I've not slammed in a letter in a rash manner. I've made it public because I didn't want to make a sneaky visit to Graham and slip it in," he said.
'Couldn't believe it'
Theresa May addresses the Commons on Monday. Image: Parliament TV
"The most unpopular option is to stay in the EU, the second most unpopular is the Prime Minister's deal. So I'm afraid, very reluctantly, after long and hard thought I just don't think she can see this through."
He added that he "could not believe it" when Ms May announced to the House of Commons that there was no deal available with the European Union that did not involve a backstop clause.
"I just couldn't believe it on Monday... she was still talking about the backstop as the solution to the Northern Ireland border. We know that's not going to get through the House of Commons."