A former Brexit minister has insisted the UK must secure a transitional deal - and that it should pay into the EU budget after we leave the bloc.
Lord Bridges, who left the government after the general election in June, urged ministers to be "honest about the task we face, and its complexity and scale", as well as "the lack of time" left to secure an agreement.
A transitional agreement would help avoid the much-feared cliff edge scenario, but should have a clear end point to avoid remaining in the EU "by stealth", he said.
The Tory peer, who campaigned for Remain, added: "We should make it clear that we are willing to continue to contribute to the EU budget as we cross the bridge - in other words, between March 2019 and the end of 2020.
"This would help us to address the EU's concern that our withdrawal blows a hole in their budget; we would be honouring commitments that we have made for the rest of the EU's budgetary period; and then the EU would need to justify why we must contribute more than this."
Lord Bridge also ridiculed Theresa May for not wanting to be defined by the process.
He told peers: "I hear talk of the government not wishing to be defined by Brexit. But Brexit is the biggest change this nation has faced since 1945.
"To say we do not wish to be defined by Brexit is like Winston Churchill saying in 1940 he did not want his government to be defined by the war. Such careless talk costs time, as it allows the machinery of government to be distracted from the task at hand.
“The priority for every department must be to help ministers get the best possible deal, prepare us for Brexit, and ensure we prosper once we have left. Nothing is more important."
The government has ruled out remaining in the single market or customs union after the point of Brexit in March 2019.