Theresa May must defy Chancellor Philip Hammond and deliver a "clean Brexit" if she is to hold the Conservative Party together, a leading Tory backbench Brexiteer has warned.
As senior ministers prepare for two days of discussions on Britain future relationship with the EU, Bernard Jenkin said Tory MPs "overwhelmingly" wanted an end to the current uncertainty.
Writing in The Sunday Telegraph, he warned the Prime Minister would only continue to command a majority in Parliament if she stuck to her present policy - which includes leaving the single market and the customs union.
His intervention came as a former Whitehall mandarin accused Brexiteers who blame civil servants for trying sabotage Britain's withdrawal from the EU of using tactics similar to those adopted by right-wing German nationalists in the 1930s.
Lord Turnbull, a former cabinet secretary and head of the civil service, compared their claims to the myth of the "stab-in-the-back" perpetuated by the German right following their country's defeat in the First World War.
"'Dolchstoss' means 'stab in the back'. After the First World War there was an armistice, but the German army was then treated as the losers. Then, at the start of the Nazi era, the 'stab-in-the back' theme developed," he told The Observer.
"It argued that 'our great army was never defeated, but it was stabbed in the back by the civilians, liberals, communists, socialists and Jews'. This is what I think these critics are trying to do.
"They are losing the argument in the sense that they are unable to make their extravagant promises stack up, and so they turn and say: 'Things would be OK if the civil service weren't obstructing us'.
"When you don't succeed, you find someone to blame for your failure."
His comments are likely to inflame the bitter war of words between some Brexiteers and elements in Whitehall who deeply resent the attacks on their impartiality.
On Saturday, the leading Tory Brexiteer Jacob Rees-Mogg accused Treasury officials of "fiddling the figures" to show that Britain would be worse off outside the EU, whatever the outcome of the negotiations.
However Mr Jenkin, who chairs the Commons Public Administration and Constitutional Affairs Committee, said that tensions among ministers were the real cause of the problem.
He said civil servants tended to take their lead from ministers, adding "what are officials meant to do" if the Prime Minister was advocating one policy and the Chancellor another.
"If ministers are vague or divided, life for officials becomes impossible, as we can see now. Ministerial collective responsibility really matters," he wrote.
His comments reflect fears amid concerns among hardline Brexiteers that Mr Hammond is leading a push within Government for a "soft" break with the EU, which could include some form of continuing customs agreement.
The Chancellor caused fury among Brexiteers when he suggested at the World Economic Forum in Davos that Britain's relationship with the EU might only change "very modestly" after leaving.
Mr Jenkin said that it was now time for all ministers to get behind the Prime Minister and support the agreed Government position.
"She can only command a majority in Parliament on her present policy. Nearly half David Cameron's MPs, voted Leave, despite his patronage and pleadings. There would have been few Remain Tories if he had advocated Leave," he wrote.
"Her MPs will back her, because we are overwhelmingly at one with the majority of the British people who now want a clean Brexit and an end to the present uncertainty.
"It is time for all her ministers to back her too and to end the confusion they are fomenting in government."