Boris Johnson’s senior adviser Dominic Cummings has accused Philip Hammond of trying to block preparations for a no-deal Brexit as chancellor.

The former Vote Leave supremo is understood to have told a meeting of Downing Street advisers that Mr Hammond and former business secretary Greg Clark had “actively frustrated” work to get the UK ready for no-deal.

But an ally of the former chancellor dismissed the claim as “simply untrue”.

Sources who witnessed Mr Cummings’ attack said: “Dom said that Philip and Greg had actively frustrated no-deal preparations. He made the point twice, and said that would not be accepted anymore.”

But an ally of the former chancellor said: “This is simply untrue.

“The bigger question is why is Dominic Cummings, the de facto deputy prime minister, so keen to spend yet more taxpayers’ money on something that his boss insists has only a ‘one in a million chance’ of happening?”

Mr Hammond and Mr Clark walked out of the government after Theresa May’s resignation rather than waiting to be sacked by her successor Boris Johnson.

Dominic Cummings (PA)

The former chancellor is reported to have held talks with Labour Brexit spokesman Sir Keir Starmer on how to use parliamentary mechanisms to frustrate efforts to take the UK out of the EU without a deal.

Mr Hammond has long been a target of criticism from fervent eurosceptics, who accuse him of failing to release sufficient funds to prepare for no-deal.