Boris Johnson is backed by speculators who have bet billions on a disorderly exit from the European Union, the ex-chancellor Philip Hammond has claimed.

In a blistering attack on the prime minister, the former Tory cabinet minister said the "radicals" advising Mr Johnson in Downing Street "do not want a deal" with Brussels.

Mr Hammond, who said he will not be attending the Tories' annual conference for the first time in 35 years, also claimed the party he first joined is "suffering a convulsion that makes it – for now at least – unrecognisable to me".

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The ex-chancellor, who had the Tory whip removed for voting against the government to block a no-deal exit from the European Union (EU), wrote in an article for The Times: "Boris Johnson asserts, ever more boldly, that we will leave the EU on 31 October, 'with or without a deal'.

"But as his sister has reminded us, he is backed by speculators who have bet billions on a hard Brexit – and there is only one outcome that works for them: a crash out no-deal Brexit that sends the currency tumbling and inflation soaring.

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1/16 The Supreme Court has ruled against Boris Johnson by declaring his government unlawfully shut down parliament for five weeks EPA 2/16 Lady Hale handed down the historic verdict, hailed by opposition MPs and anti-Brexit campaigners. She said all 11 judges were unanimous in deciding that the case is “justiciable”, so the government loses that part of the argument. “The court is bound to conclude therefore that the decision to advise Her Majesty to prorogue was unlawful because it had the effect of frustrating or preventing the ability of Parliament to carry out its constitutional functions.” EPA/Supreme Court 3/16 Gina Miller and her team react outside the Supreme Court are the verdict. She said: “Today is not a win for any individual or cause. It is a win for Parliamentary sovereignty, the separation of powers and independence of our British courts. Crucially, today’s ruling confirms that we are a nation governed by the rule of law, laws that everyone, even the Prime Minister, are subject to." PA 4/16 A person dressed as a caricature of British Prime Minister Boris Johnson in a prison uniform stands outside the Supreme Court AP 5/16 Labour leader Jeremy Corbyn called for Mr Johnson to “consider his position” following the landmark decision, while Lib Dem leader Jo Swinson said he was “not fit to be prime minister” Getty 6/16 Scottish National Party (SNP) Westminster leader Ian Blackford raises his arms as he comes outside. He said: "This is an absolutely stunning judgement by the Supreme Court today." He went on to say, "we all want to get back to work, and quite frankly, on the back of this, Boris Johnson must resign immediately." AFP/Getty 7/16 Crowds outside celebrated the verdict AP 8/16 Delegates at the Labour party conference applaud after hearing the news AFP/Getty 9/16 Speaker John Bercow said MPs must now “convene without delay” and confirmed the Commons would return at 11.30am on Wednesday AFP/Getty 10/16 Gina Miller said: "“As a result of this judgment, Parliament is open, it was never prorogued. I urge MPs to get back to work immediately.” AP 11/16 MPs Anna Soubry, Liz Saville Roberts and Caroline Lucas, together with SNP leader Ian Blackford, react. Green MP Caroline Lucas has said the Supreme Court’s decision is “just the start” Reuters 12/16 “The UK deserves a Prime Minister and a Government who act with honesty, integrity and in a manner consistent with our constitution, at all times." AFP/Getty 13/16 AP 14/16 The SNP’s Joanna Cherry QC says: “Boris Johnson’s position is untenable and he should have the guts to resign.” PA 15/16 EPA 1/16 The Supreme Court has ruled against Boris Johnson by declaring his government unlawfully shut down parliament for five weeks EPA 2/16 Lady Hale handed down the historic verdict, hailed by opposition MPs and anti-Brexit campaigners. She said all 11 judges were unanimous in deciding that the case is “justiciable”, so the government loses that part of the argument. “The court is bound to conclude therefore that the decision to advise Her Majesty to prorogue was unlawful because it had the effect of frustrating or preventing the ability of Parliament to carry out its constitutional functions.” EPA/Supreme Court 3/16 Gina Miller and her team react outside the Supreme Court are the verdict. She said: “Today is not a win for any individual or cause. It is a win for Parliamentary sovereignty, the separation of powers and independence of our British courts. Crucially, today’s ruling confirms that we are a nation governed by the rule of law, laws that everyone, even the Prime Minister, are subject to." PA 4/16 A person dressed as a caricature of British Prime Minister Boris Johnson in a prison uniform stands outside the Supreme Court AP 5/16 Labour leader Jeremy Corbyn called for Mr Johnson to “consider his position” following the landmark decision, while Lib Dem leader Jo Swinson said he was “not fit to be prime minister” Getty 6/16 Scottish National Party (SNP) Westminster leader Ian Blackford raises his arms as he comes outside. He said: "This is an absolutely stunning judgement by the Supreme Court today." He went on to say, "we all want to get back to work, and quite frankly, on the back of this, Boris Johnson must resign immediately." AFP/Getty 7/16 Crowds outside celebrated the verdict AP 8/16 Delegates at the Labour party conference applaud after hearing the news AFP/Getty 9/16 Speaker John Bercow said MPs must now “convene without delay” and confirmed the Commons would return at 11.30am on Wednesday AFP/Getty 10/16 Gina Miller said: "“As a result of this judgment, Parliament is open, it was never prorogued. I urge MPs to get back to work immediately.” AP 11/16 MPs Anna Soubry, Liz Saville Roberts and Caroline Lucas, together with SNP leader Ian Blackford, react. Green MP Caroline Lucas has said the Supreme Court’s decision is “just the start” Reuters 12/16 “The UK deserves a Prime Minister and a Government who act with honesty, integrity and in a manner consistent with our constitution, at all times." AFP/Getty 13/16 AP 14/16 The SNP’s Joanna Cherry QC says: “Boris Johnson’s position is untenable and he should have the guts to resign.” PA 15/16 EPA

"So they, at least, will be reassured to see no evidence at all that his government has seriously pursued a deliverable deal; still less that it has been pursuing a deal that could get us out by 31 October."

Speaking earlier this week Rachel Johnson, the prime minister's sister, was asked on BBC Radio 4's World at One who could be behind the strategy to deliver Brexit in any shape or form.

She replied: "It could be Dominic Cummings advising the prime minister to be extremely aggressive and to face down opposition from all sides of the establishment in order to secure his position as the tribune of the people."

Ms Johnson continued: "It could be coming from my brother himself, he obviously thoroughly enjoys being prime minister. It could be from – who knows – people who have invested billions in shorting the pound or shorting the country in the expectation of a no-deal Brexit. We don't know."

Downing Street declined to comment on Mr Hammond's remarks on the eve of the party's annual conference when approached by The Independent, but business minister Nadhim Zahawi said they were "completely untrue".

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"Philip you let yourself down by claiming speculators on 'no deal' are interfering in us leaving the EU. This is an ugly smear that is completely untrue. If you know anything about finance or the City then you will know that," he said.

Labour MP David Lammy, however, claimed: "It's official. Philip Hammond in today's Times confirming that Boris Johnson is committed to a hard Brexit because the disaster capitalists who backed his campaign will make money millions."

In his article for The Times, Mr Hammond added of his party: "Gone is the relaxed, broad-church coalition, united by a belief in free-trade, open markets, fiscal discipline and a fear of the pernicious effects of socialism, but tolerant of a wide range of social and political opinion within its ranks.

"In its place is an ideological puritanism that brooks no dissent and is more and more strident in its tone."