Britain's Brexit Secretary David Davis has warned Labour MPs they risk creating chaos and uncertainty if they scupper the government's plans for transferring laws from Brussels to Britain.
Mr Davis said dissension in a key Commons vote on the Great Repeal Bill tomorrow would be "simply an attempt to thwart the democratic process", urging MPs on all sides to back the legislation.
Writing in the Sunday Telegraph, Mr Davis insisted negotiations with Brussels were "delivering steady progress" on issues like citizens' rights and the Irish border.
He said it is "not a moment to go backwards", dismissing criticism of the government's flagship bill as "vacuous".
"Any broad attempt to block the Bill, without any sense of a viable alternative, is simply an attempt to thwart the democratic process," Mr Davis wrote.
"So, as my colleagues in the House of Commons proceed through the voting lobbies tomorrow, they must remember what they are voting for.
"They are not voting on whether or not we leave the EU. That decision was made by the British people last June.
"Nor are they voting for the terms of our exit. Those will be agreed as we proceed through our negotiations with the EU.
"What they are voting on is how we leave: whether our withdrawal is smooth and orderly, or chaotic and uncertain."
The rallying call came after Labour denounced the Great Repeal Bill as an undemocratic "power grab" by ministers.
Accusing opposition MPs of only contributing "moan, complaint and gripe" to the Brexit debate, Mr Davis insisted that laws contained within the mammoth bill would not allow the government to bypass Parliament.
Meanwhile, former British prime minister Tony Blair has called for tough new immigration rules which would allow Britain to exercise more control over who comes into the country without leaving the European Union.
Mr Blair admitted the open borders he presided over are no longer appropriate and put his name to a report calling for tighter domestic controls and the negotiation of modified free movement rules with the EU.
This would fulfil the will of the people expressed in last year's Brexit vote while allowing Britain to stay in the EU, and Jeremy Corbyn's Labour should back the approach, he said.