JO Johnson has turned his fire on brother Boris after quitting the Cabinet yesterday, accusing the former Foreign Secretary of making false promises during the Leave campaign.

The junior transport minister issued a searing critique of Theresa May's Brexit deal on Friday when he unexpectedly quit - but he has now attacked his older brother with a thinly-veiled swipe.

Speaking on BBC Radio 4 this morning, when asked about Boris' role in Brexit, he said: "In the Leave campaign there were undoubtedly promises made that have been shown to be undeliverable.

"No one can dispute that."

The younger Johnson said Britain needed to pull back from the brink and have a second referendum on leaving the EU.

He also said he knew other ministers and lawmakers were "reflecting hard" on whether to quit in protest at Theresa May's Brexit plan after his dramatic resignation ramped up pressure on the PM.

Johnson had previously voted to remain in the EU, and his departure risks galvanising other pro-EU ministers to oppose May's deal, alongside the Brexiteers within the ruling party who have already said they will not vote for the plan.

"I know many are reflecting hard about the deal that's looming and how they will respond to it, but it's obviously for each of them to work out how best to respond," he added.

"This is one of the most momentous questions we will ever face in our political careers. It's up to (lawmakers) to take a stand. I've done so, if others feel that it's right for them to do so then good on them."

Johnson said there was now a huge gulf between the type of Brexit that was promised by his brother Boris, a leading campaigner to leave the EU, and the deal that May is hammering out in Brussels.

As a result, he said it would be a "democratic travesty" if the government did not consult the public on whether they still wanted to leave the world's largest trading bloc.

Jacob Rees-Mogg, a leading Brexiteer in May's party, told BBC Radio he rejected the call for another referendum but agreed with the criticism of the deal. He said in its current form it would not have enough Conservative support to get through a vote in parliament.