WESTMINSTER can still stop a no-deal Brexit, Philip Hammond has insisted, but warned that if Britain did crash out of the EU without a deal, it would do “potentially irreparable damage” to the Union of the United Kingdom.

The former Chancellor suggested that Boris Johnson was not in control of the UK Government’s Brexit strategy and that the likes of Dominic Cummings – the former Leave campaign chief who is now the Prime Minister’s chief adviser – were running the show.

But he was accused by Iain Duncan Smith, the former party leader, of the “political crime” of not preparing adequately for a no-deal, which meant the EU could dictate the terms of Britain’s departure.

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In his first major intervention into the Brexit debate since resigning as Chancellor just before Mr Johnson took over in Downing St, Mr Hammond claimed leaving the EU without a deal would be a betrayal.

“It would be just as much a betrayal of the referendum result as not leaving at all,” declared the former Cabinet minister.

“The British people were offered a proposition that we could leave the EU while having a close relationship. They were told it would be the easiest deal ever done. All the evidence points to people wanting to maintain a close trading relationship with the EU to protect British jobs and British prosperity and minimise disruption in the future.

“To set the bar for negotiations so high that we inevitably leave without a deal would be a betrayal. The Prime Minister said he would get a deal and we want to see him deliver that deal,” he told BBC Radio 4’s Today programme.

He went on: “Pivoting to say that the backstop has to go in its entirety, a huge chunk of the Withdrawal Agreement just scrapped, is effectively a wrecking tactic and the people behind this know that that means there will be no deal.”

Asked who he meant by “people behind this,” the former Chancellor explained: “Those who are pulling the strings in Downing St, those who are setting the strategy. Boris Johnson has told me privately and he has told the country publicly that he is determined to get a deal and is confident that he can get one. But I fear there are people around him whose agenda is different.”

When it was suggested it was unfair to blame Mr Cummings for the PM’s strategy, Mr Hammond said: “It is the PM’s strategy to get a deal. He’s told us he is confident of that, that the chances of no-deal are less than one in a million. We now need to see steps being taken to operationalise that commitment. I want to see Boris Johnson delivering a great deal for Britain. I want to be backing him all the way to make this a successful Conservative government and so do my like-minded colleagues.”

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Asked what he would do to stop a no-deal outcome, Mr Hammond stressed the parliamentary arithmetic had got slightly worse from the PM’s viewpoint.

“Boris Johnson is in the same position that Theresa May was in; he has to listen to Parliament and Parliament is clearly opposed to a no-deal exit and the PM must respect that; this is a parliamentary democracy…

“I’m confident Parliament has a clear view on this and it has the means to express that view.”

When it was put to him to stop a no-deal MPs would have to pass a new law, which could be very difficult, the former Chancellor stressed: “I am very confident that the means exist for Parliament to make its voice heard and to pass legislation that gives effect to the clear view of Parliament. Of course, the mechanisms being there does not necessarily and automatically deliver you the majority; in a parliamentary democracy everything depends on whether there is a majority of MPs to support something."

He went on: “It’s very clear to me – and the Speaker has also been very clear – that if a majority of MPs clearly wants to go down a certain route, a means will be delivered to allow that to happen…

“Any idea of trying to bypass Parliament by dissolving it and holding an election over the exit date would provoke a constitutional crisis. We have an unwritten constitution but the principles behind it are very clear and one of them is that an outgoing government should not act in a way to prevent an incoming government from making key decisions.”

As revealed by The Herald yesterday John Bercow, on the Edinburgh Fringe festival, said he would “fight with every breath in my body" any attempt by the PM to suspend Parliament to force through a no-deal Brexit against MPs' wishes.

He made clear he "strongly" believed the Commons "must have its way", adding: “If there is an attempt to circumvent, to bypass or - God forbid - to close down Parliament, that is anathema to me. I will fight with every breath in my body to stop that happening."

Mr Hammond argued that more than 17 million, who voted for Brexit in the 2016 referendum, did not do so to exit the EU without a deal.

“That’s the key point,” he declared. “There is no mandate for leaving with no-deal. It’s absurd to suggest the 52 per cent of people who voted to leave the EU all voted to leave with no-deal when in fact during the referendum campaign there was virtually no mention made by the leaders of that campaign at all of the possibility of leaving without a deal. Michael Gove himself said earlier this year that the campaign he led did not offer the prospect of a no-deal exit.”

The former Chancellor stressed that the May Government had done much to prepare for a no-deal, having spent £4.2 billion and claimed that Downing St’s assertions to the contrary were not true.

He added that a no-deal exit would “cause significant harm to the UK economy and potentially irreparable damage to the Union of the United Kingdom; people need to know the facts”.

But Mr Duncan Smith accused Mr Hammond of doing "nothing to prepare us for leaving with no-deal".

He told Today: "By not preparing to leave with no-deal, they made it certain that we'd have to swallow everything that the European Union gave us.

"So, the crime that has been committed, in political terms, was committed by him and those who did not prepare us to leave," the Scot added.