Michael Heseltine has launched a scathing attack on Theresa May's handling of Brexit which he said has left a huge number of Tories feeling "appalled and betrayed".
The Conservative former deputy prime minister dismissed comments by Boris Johnson that it would be fine for the UK to crash out of the EU without a deal as "rubbish".
And Lord Heseltine – who was last week sacked as a Government adviser for rebelling over Brexit – insisted he will stay in his party "and fight".
Speaking to ITV's Peston on Sunday, he said Zac Goldsmith's defeat in the Richmond by-election last year is far more significant than the Conservative Party's "fluky" win in Copeland, where Labour suffered an historic defeat.
He said: "You should see my postbag. My postbag is from that very, very large minority – almost half – many of whom are bitterly disappointed with the Tory Party.
"You shouldn't be talking about a fluky by-election on the nuclear industry in the north of England, you should be talking about Richmond. See what happened there, where Europe was the central issue.
"And the fact is that a huge number of Conservatives are appalled, they feel they have been betrayed by what is going on now.
"The truth of the matter is, those of us in politics, those who care, we are not performing fleas where the ringmaster says 'jump' and we all turn hands up over ourselves. We are not like that.
"We happen to believe, for all sorts of very powerful reasons, that British self-interest was inextricably interwoven with those of our European allies."
Pressed on whether he would ever resign from the Tory Party, the former Cabinet minister said he will stay "and fight".
He told the show: "I remember this phrase I think – pick your party, damn your principles.
"Well I hope I don't damn my principles but I won't leave my party."
He said it was a mistake for the 'Gang of Four' to leave the Labour Party and set up the SDP in the 1980s, and said: "I will stay there (in the Tory Party) and fight."
Lord Heseltine was also dismissive of Mr Johnson's claims it would be "perfectly OK" for Britain left the EU without a deal, describing the comments as "rubbish".
And he vowed to continue to campaign to convince the British public of the perils of leaving the European Union.
Coining a phrase from Conservative prime minster Harold Macmillan, Lord Heseltine said he believed people may change their minds because of "events, dear boy, events".
He said the consequences of the leave vote have been masked by the short-term boost arising from the devaluation of the pound.
But he warned that tough economic times lie ahead as the British economy is being sustained by a splurge in consumer spending.
He said: "It is like 2008 all over again."
Lord Heseltine also revealed that he has still not heard from Mrs May following his dismissal as a Government adviser on industrial strategy.
He told the show he is "very sad" to no longer be working with the Government on its policy.
He said: "I spent the last six years helping Tory ministers in pursuing, what I believe domestically, are at the heart of the need to rebuild our economy – to break the monopoly of London, to empower the local economies, to create an opportunity where the public and private sectors work together as opposed to slagging each other off.
"And we have made a lot of progress, but Theresa May took the view that that would come to an end, and she is entitled to do that."
He said all his conversations about the sacking have been with the party's chief whip in the Lords.