Brexit Secretary David Davis has accused Labour of threatening to “delay, bog down and defeat” the Government’s repeal bill which goes before MPs this week.
The first full parliamentary debate on the legislation is set for Thursday but the Labour Party is expected to push for changes which would keep the UK in the single market and customs union during a transition period after 2019.
As Theresa May moves to prevent a rebellion from Remain-supporting MPs within her own party, her allies have sent warnings to those who might be tempted to rebel and help the Labour effort.
Mr Davis, writing in the Sun on Sunday, said: “(Labour leader) Jeremy Corbyn’s unscrupulous Labour Party are threatening to delay, bog down and defeat this essential piece of legislation.
“Their only motivation is the pursuit of chaos.”
He added: “The uncertainty our exit from the EU would cause without legal continuity is only matched by the total instability of Labour’s position on Brexit.
“They offer no ideas and no solutions.
“In the 14 months since Britain voted to leave the EU, Labour have put forward 10 different Brexit plans and one big mess.”
Damian Green, the First Secretary of State and Mrs May’s de facto deputy, wrote in The Sunday Telegraph that it was “the job of all MPs, including my former colleagues on the Stronger In campaign, to respect the will of the people and get the best possible deal for Britain”.
He added: “No Conservative wants a bad Brexit deal, or to do anything that increases the threat of a Corbyn government.”
But pro-Remain Tory Anna Soubry said the warnings would “backfire”.
She told The Observer: “Any suggestion that this is in any way treacherous or supporting Jeremy Corbyn is outrageous.
“It amounts to a trouncing of democracy and people will not accept it.”
Mrs May herself warned MPs that the UK could be faced with a Brexit “cliff edge” if they refuse to back her EU repeal bill.
Ahead of the debate, she said: “Now it is time for Parliament to play its part.
“The Repeal Bill delivers the result of the referendum by ending the direct role of the EU in UK law, but it is also the single most important step we can take to prevent a cliff-edge for people and businesses, because it transfers laws and provides legal continuity.”
Meanwhile, Downing Street has denied a report that Theresa May is prepared to pay a £50bn divorce bill to the EU.
The report in The Sunday Times quoted an unnamed source as saying that the plans would see the UK pay between £7bn and £17bn a year for three years after Brexit.
Sky News Senior Political Correspondent Jason Farrell said he had been unable to verify the claims and Number 10 sources rejected the story as “not true”.