Former deputy prime minister Lord Heseltine will warn politicians that Britain’s youth will “never forgive us” unless they are offered the chance to reverse Brexit.

The Conservative veteran, 85, will address a rally calling for a second referendum ahead of Tuesday’s crunch Commons vote on Theresa May’s Brexit deal.

He will claim that the government appears to have “lost control” and there were signs that MPs were prepared to take action to “assert the authority” of parliament.

Highlighting a generational split in the result of the 2016 referendum, he will say “those of a certain age who voted 70:30 to leave” are “rapidly being replaced by a younger generation who voted 70:30 to stay”.

At the rally in London’s ExCel centre, which will also be addressed by politicians including Liberal Democrat leader Sir Vince Cable, Tory former ministers Anna Soubry and Philip Lee, and celebrities including Charles Dance and Jason Isaacs, Heseltine will claim that those campaigning for a second vote are “British patriots” who are “proud of our Commonwealth and empire”.

The event, organised by the Best for Britain and People’s Vote campaigns, will feature politicians from the Tories, Labour, Liberal Democrats, Green party and Plaid Cymru.

Heseltine will hit out at Brexiters who have called pro-EU politicians “traitors”, saying: “May our opponents never be forgiven for their allegations that it is us who are letting Britain down.”

He will say: “Let us make our position clear. We are the British patriots. We want a Britain at the heart of Europe because we want the voice of Britain, the tolerance of Britain, the culture of Britain, at the heart of Europe. We are proud of our Commonwealth and empire. Our voice is their voice in Europe.

“It is the Brexiteers who seek to belittle us, to undermine our influence, to slam windows, to close doors with the suggestion that our membership of the European community blunts our influence.”

In comments echoing a youthful William Hague’s address to the Tory conference in 1977, when he told his ageing audience “half of you won’t be here in 30 or 40 years’ time” as he discussed the future, Lord Heseltine will say: “Let me repeat his warning. Let me paraphrase his words. ‘I certainly won’t be here.’ But neither will my generation.

“The parents, the grandparent will have gone. The younger generation, they will be here. They will be here.

“They will never forgive us if we now exclude them from the corridors of European power. Offered a seat in an anteroom as others decide behind closed doors. Invited to submit their views in writing so others may decide behind closed doors.

“Trying to negotiate trade deals on behalf of the United Kingdom in competition with a European Union six times our size offering bigger, better deals behind closed doors.”

Heseltine will add: “No one can predict the events of next week. Every news bulletin, every headline, every leak tells us of a government that has lost control. These are the first promising signs that a growing number of members of the House of Commons are prepared to assert the authority and sovereignty of that place.

“Our country’s future depends on their judgment and will. They must act in the national interest. Their conclusions must be put back to the people for their endorsement.”

Meanwhile, Nigel Farage has said in an article for the Sunday Telegraph that he could launch a new political party and fight the 2019 European election if Brexit is delayed.

Just days after quitting Ukip, the party he led to victory in the 2014 European elections, Farage said he was “thinking about vehicles” to contest the elections next year if the UK is still in the European Union.

“I am not going to lie down and watch it go down the plug hole. I couldn’t do that. And I won’t do that.”

He said the move would be “the birth of something much more remarkable than Ukip was”.