Jo Johnson says colleagues are considering their position over Brexit

The junior transport minister - and younger brother of former Foreign Secretary Boris Johnson - issued a searing critique of May’s Brexit deal on Friday when he unexpectedly quit, saying the country needed to pull back from the brink.

On Saturday he also attacked the “fantasy set of promises” made during the referendum by Brexit campaigners such as his brother.

The gulf between their vision and the one proposed by May was now so vast, he said, that it would be a “democratic travesty” if the public was not consulted in a new vote.

“This is one of the most momentous questions we will ever face in our political careers,” he told BBC Radio on Saturday.

“I know many are reflecting hard about the deal that’s looming and how they will respond to it.”

Jo Johnson’s intervention was all the more powerful because he had previously voted to remain in the bloc. His departure risks galvanising other pro-EU ministers against the deal, alongside Brexiteers who have already vowed to vote against it.

The criticism underscores the battle that lies ahead as May tries to strike a deal that will be acceptable to the different factions in her deeply divided party and the small Northern Irish Democratic Unionist Party that she relies on to govern.

May has prioritised maintaining the free trade of goods with Europe, but her many critics say that will leave Britain subject to decisions made in Brussels without any input from London.

Talks with EU negotiators are due to resume on Sunday. Less than five months before Britain is due to leave the EU on March 29, negotiations are still stuck over a backup plan for the land border between British-ruled Northern Ireland and EU member Ireland, should they fail to clinch a long-term deal.

“It’s close but everything is hanging by a thread because of the political situation in the UK,” one diplomat familiar with an EU briefing of national envoys on Friday told Reuters.

The DUP’s leader Arlene Foster said on Saturday her 10 lawmakers could not vote for the deal because it would “handcuff the UK to the EU, with the EU holding the keys”.

Trade minister Liam Fox, Britain’s trade minister, said Britain may not agree a deal if a solution cannot be found.

Jo Johnson, a former Financial Times journalist with a much lower profile than his brother, said he could not accept that parliament should have to choose between May’s deal and no deal, which would imperil the economy.

He said May’s proposal put the country on the brink of the greatest crisis since World War Two and that his priority was to stop the country from doing something “irrevocably stupid”.

“In the campaign there were undoubtedly promises made that have been shown to be undeliverable,” he said.

“They are so radically different from the Brexit that was billed during the referendum that I think it would be a democratic travesty if we did not go back to the people and seek their consent for our departure from the EU on this basis.”

Downing Street has said there will be no second referendum.