Former Chancellor Philip Hammond has accused the PM of trying to wreck the chance of a new Brexit deal, by making demands the EU could never accept.
In a Times article, Mr Hammond said a no-deal Brexit would be “a betrayal” of the 2016 referendum result.
He told the BBC he was “confident” that Parliament “has the means” to express its opposition to a no-deal exit.
A No 10 source said the UK would leave on 31 October despite Mr Hammond’s “best efforts to the contrary”.
The source added that Mr Hammond, as chancellor, “did everything he could” to block preparations for leaving and had “undermined negotiations”.
The former chancellor rejected this suggestion in a tweet, saying he wanted to deliver Brexit “and voted to do so three times”.
Prime Minister Boris Johnson has said he wants to leave the EU with a deal, but the UK must leave “do or die” by the latest Brexit deadline of 31 October.
He wants the EU to ditch the Irish border backstop plan from the deal negotiated by former PM Theresa May, which was rejected three times by Parliament.
But the EU has continued to insist that deal, including the backstop arrangements, is the only agreement possible.
Many of those who voted against the deal had concerns over the backstop, which if implemented, would see Northern Ireland staying aligned to some rules of the EU single market.
It would also see the UK stay in a single customs territory with the EU, and align with current and future EU rules on competition and state aid.
These arrangements would apply unless and until both the EU and UK agreed they were no longer necessary. Read more