Lord Heseltine has admitted he and fellow Remain supporters have "lost" following Boris Johnson's general election victory and dismissed the prospect of "fighting on".
The former Conservative deputy prime minister had urged voters to back the Liberal Democrats, or independent candidates who had been expelled from the Tories by Mr Johnson, prior to Thursday's ballot.
But, speaking to Sky News on Saturday, Lord Heseltine admitted his message hadn't got through to enough voters after Mr Johnson secured a crushing 80-strong majority.
The peer said: "They didn't listen because they wanted to get out of the austerity and they saw Brexit as a route to do that.
"We've lost, we have to face up to that, we're going to leave Europe."
Lord Heseltine himself had the Tory whip withdrawn earlier this year for saying he would "experiment" with voting for the Lib Dems during the European Parliament elections.
The ex-cabinet minister was a supporter of the People's Vote campaign for a second EU referendum.
But Lord Heseltine has now joined other leading figures in abandoning that campaign as the prime minister prepares to put his Brexit deal through parliament.
He said: "The reality is Boris Johnson has got a thumping parliamentary majority and there's no way they will not get their legislation through in very short order - so we will leave the EU.
"We've then got a period of uncertainty but, frankly, it's pie in the sky to talk about fighting on in the present circumstances.
"I have no doubt at all my fellow peers in the House of Lords will take the same view.
"We are not there to defy the will of the people."
On Friday, Open Britain - the successor to the official Remain campaign at the 2016 EU referendum - said it would "rebrand" in the New Year and push for a "fair deal for Britain" as the country leaves the EU.
The group said: "The People's Vote will now refocus its campaign to concentrate on vital social issues that this Government must urgently prioritise in its Brexit.
"We urge the government to avoid a hard Brexit that will be a disaster for our country and instead work with our European partners to get the fair deal that British people deserve.
"The poorest and most vulnerable will be further marginalised if Boris Johnson's government crashes us out of the EU with no deal.
"Early next year, the People's Vote campaign will rebrand and reorganise to campaign for a fair deal for Britain."