Dominic Cummings targeted as Hammond claims Boris Johnson allowing 'unelected people' to 'pull the strings' in Number 10

Former chancellor says no-deal Brexit 'just as much of a betrayal' of referendum result as not leaving EU at all

Philip Hammond has launched a blistering attack on Boris Johnson, saying the new prime minister is allowing "unelected people" to "pull the strings" in Downing Street.

The former chancellor condemned "absurd" claims from Eurosceptic "hardliners" about a no-deal Brexit and said the first weeks of the new government were "not encouraging".

His comments will be seen as an attack on Dominic Cummings, Mr Johnson's top policy adviser.

Mr Hammond, one of the most senior MPs working to block a no-deal Brexit, also criticised Dominic Raab, saying the foreign secretary's claim that the public had voted for such an outcome was "a total travesty of the truth".

The intervention represents a stepping up of Tory backbench efforts to stop Mr Johnson taking Britain out of the EU without a deal.

Rebels have been plotting across party lines to try to come up with a plan to block no-deal when MPs return from their summer break in early September.

John Bercow, the Commons speaker, insisted on Tuesday that MPs could stop a no-deal exit and said he would fight "with every bone in my body" to block any attempt to close parliament to force one through.

Mr Hammond said Mr Johnson's demand that the EU scrap the controversial Northern Ireland backstop part of the current Brexit deal amounted to a "wrecking" strategy.

Writing in The Times, he said: "The unelected people who pull the strings of this government know that this is a demand the EU cannot and will not accede to.

"Not just because they will be stubborn in their defence of the single market (although they will) but because the fragility of their own coalition of 27 means that any attempt on their side to reopen the package would see their unity collapse. They will not take that chance and the smart people in Whitehall know it."

Mr Johnson has insisted that he will deliver Brexit by 31 October "whatever the circumstances" and has ramped up government planning for no-deal.

Despite the fast-approaching deadline, he has not yet held any face-to-face talks with EU leaders about amending the current deal. Meetings are expected to take place at the G7 summit in Biarritz later this month.

Mr Hammond insisted that no-deal was "not an acceptable outcome" and criticised Mr Raab's suggestion that the public had voted for it when they backed Leave in 2016.

He said: "In 2016 the British people were invited to vote for Brexit with a deal, and by a small margin they did so. They were told that a deal to protect Britain's trade with the EU - our largest export market by far - would be 'easy' to do.

"To pretend now that 2016 Leave voters voted for a hard no-deal Brexit is a total travesty of the truth.

"As the BBC's 'reality check' had to remind Dominic Raab, now the foreign secretary, the possibility of no-deal was not 'regularly raised' during the referendum campaign."

He added: "Michael Gove put it best in March this year when he said: 'We didn't vote to leave without a deal. That wasn't the message of the campaign I helped lead'."

Mr Hammond later told BBC Radio 4's Today that "leaving the European Union without a deal would be just as much of a betrayal as not leaving at all" and insisted that "a means will be delivered" to allow MPs to block no-deal.

The former chancellor is one of 20 Tory MPs, including six former cabinet ministers, who have written to Mr Johnson warning that his demands on the backstop "set the bar so high that there is no realistic prospect of a deal being done", according to reports.