Brexiteers responsible for persuading the British to leave the European Union will never be forgiven for their “false promises”, Sir John Major has warned.

The former prime minister described the 2016 referendum vote as a “colossal misjudgement” that would leave the country poorer and weaker.

In a lecture in London, he said that once people understood they had been deceived, those responsible would have “much to answer for”.

“We know the post-Brexit world will be very different from now. It cannot be otherwise, because no form of Brexit will remotely match up to the promises made by the Leave campaign in the referendum: they were vote-gathering fantasies, not serious politics,” he said.

“It will damage our national and personal wealth, and may seriously hamper our future security.  It may even, over time, break up our United Kingdom. It will most definitely limit the prospects of our young.

“And – once this becomes clear – I believe those who promised what will never be delivered will have much to answer for. They persuaded a deceived population to vote to be weaker and poorer.

“That will never be forgotten – nor forgiven.”

In comments likely to be seen as a thinly veiled sideswipe at Boris Johnson, Sir John – a long-standing opponent of Brexit – hit out at the political “princelings” vying for the Tory crown.

He warned their “belligerent noises off” were making Theresa May’s task of negotiating a deal with Brussels even more difficult, while those whose focus was on self-advancement were “rarely the most suitable to be entrusted with power.”

“What government is not about is cheap grandstanding. It’s not about deceiving the electorate with slogans, or soundbites, or untruths or half-truths. It’s not about windy oratory that says nothing,” he said.

“And – most emphatically – it’s not about princelings fighting for the political crown of premiership.  Coded messages that shriek ‘I’m the one’ are about as subtle as a punch on the nose.”

Sir John also voiced concern that as the extremes of right and left gained strength, the moderate “centre vote” would lose its traditional influence over policy.

“Our nation should not tolerate the unreasoning antipathy of the extremes – to the EU, to foreigners or to minority groups,” he said.

“Such antipathy is repellent, and diminishes us as a nation. Softer, more reasonable voices should not be drowned out by the raucous din of the loudest.

“I freely confess to a taste for compromise. I have always preferred good old British pragmatism to rigorous ideology. Politics is real life.

“It isn’t warfare. It isn’t a popularity contest. It’s about people. It’s about four nations who deserve more than an ideological tug-of-war.”