Referring to the ERG, the minister told The House magazine: “The prime minister has done a pretty good job of standing up to them up till now, but they were drinking champagne to celebrate her losing her deal and I regard that as being treachery.”
He added: “I read that Nigel Farage is setting up a new party called ‘Brexit’ and if I were them I’d be looking at that, because that seems to reflect their views more than the Conservative Party does.
“They should read carefully what that party’s got to offer, because in my view they’re not Conservatives.
“There are people who are very solid and stringent in their views and if I were they I would be looking at a party that seems designed for them – Nigel Farage’s party.”
Mr Harrington, who backed Remain in the referendum, said it would give the ERG pleasure if ministers who shared his views on Brexit resigned.
He said: “If we all resigned what would then happen?
“If I were in the ERG, it would give me a lot of pleasure to see us resign.
“But we can’t give in to a minority of a minority, which is what the ERG are.”
Mr Harrington also dismissed the so-called Malthouse compromise, which is intended to try to bridge Tory divisions on Brexit.
The minister said: “It’s basically regurgitated Canada-plus, which we know is not at all suited to our close relationship with the European Union, plus a bit of glorified number plate recognition kit, which they’ve got there anyway.
“I think it’s just fanciful nonsense.”
Mr Harrington has previously declared he is happy to be sacked by Theresa May if she objects to him speaking out about the dangers of leaving the EU without an agreement on 29 March.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies