Blocking Brexit could lead to a surge in far-right extremism in the UK, a cabinet minister has said.
Transport Secretary Chris Grayling told the Daily Mail that not leaving the EU would cause the 17 million people who voted for Brexit to feel "cheated".
This could end centuries of "moderate" politics in the UK, he said, as he urged his colleagues to back Prime Minister Theresa May's Brexit deal.
A vote on the agreement takes place in the Commons on Tuesday.
MPs are widely expected to reject the deal, negotiated between the EU and UK, with more than 100 Conservative MPs among those opposing it.
Some ministers have warned the UK faces Brexit "paralysis" if this happens.
'Nastiness in politics'
Just days before the critical vote, Mr Grayling, who campaigned to leave the EU, told the Daily Mail there would be a "different tone" in British politics if the UK failed to leave the EU, and predicted a "less tolerant society" and a "more nationalistic nation".
"It will open the door to extremist populist political forces in this country of the kind we see in other countries in Europe," Mr Grayling told the paper.
"If MPs who represent seats that voted 70% to leave say 'sorry guys, we're still going to have freedom of movement', they will turn against the political mainstream," he added.
"There's already a nastiness and unpleasantness in our politics, more people with extreme views, more people willing to behave in an uncivilised way," he said.
Lord Hattersley, a former deputy Labour Party leader, dismissed Mr Grayling's comments, saying not many would regard him as "an expert in these matters".
He told BBC Radio 4's Today programme that he did not believe a general election - which Labour leader Jeremy Corbyn has pushed for - would happen.
Lord Hattersley, a minister in the Wilson and Callaghan governments, called for another referendum, saying the party had to risk losing the support of Labour supporters who voted to leave the EU in order to do the "right" thing.
Mr Grayling's intervention comes after his Conservative colleagues warned about the possibility of the UK leaving the EU with no deal.
Northern Ireland Secretary Karen Bradley said a no-deal exit would create a "feeling of unrest".
Tory rebel Dominic Grieve, who tabled the amendment that led to a second government defeat on Brexit last week, urged the prime minister to delay Brexit if her EU deal was rejected by MPs.
Mr Grieve is among a group of MPs calling for another referendum.