Legislation to allow Britain to choose which bits of European Union law it keeps after Brexit must not be rushed through Parliament like the Bill to authorise Theresa May to trigger exit negotiations, a parliamentary committee has said.
The House of Lords Constitution Committee said it recognised the "political imperatives" that lie behind the fast-tracking of the European Union (Notification of Withdrawal) Bill.
But it warned that the accelerated timetable, with less time allowed between different stages in the Commons and Lords, should not set a precedent for the so-called Great Repeal Bill, which will transpose all EU law into UK law, giving Parliament the power to decide which bits to keep.
The EU (Notification of Withdrawal) Bill was tabled after the Supreme Court ruled last month that the Prime Minister must get authority from MPs and peers before triggering Article 50 to begin Brexit negotiations.
It was first debated by MPs on January 31 before being fast-tracked through the Commons.
The Bill will enter its second Lords stage, committee, next week and is scheduled to finish its passage through the upper chamber on March 7.
A period of parliamentary "ping pong" may follow but Mrs May expects to be able to stick to her timetable of invoking Article 50 by April.
Committee chairman Lord Lang of Monkton said: "The European Union Withdrawal Bill is undeniably of significant constitutional importance.
"Usually we would be concerned about the fast-tracking of constitutional legislation, particularly when the justification for doing so depends on a political, rather than constitutional, deadline.
"However, we recognise the political imperatives that underlie this Bill. In addition, any concerns we might have about the curtailment of parliamentary scrutiny are mitigated by the fact that the Bill is very short and straightforward.
"We have made clear, however, that this should not set a precedent for future constitutional legislation.
"The Great Repeal Bill and other Brexit-related legislation will be much more complicated, and we would expect that Parliament will have the opportunity fully to scrutinise such important legislation."
Meanwhile, amid reports that ministers were considering a concession to peers, who are threatening to inflict a defeat on the Government over giving Parliament a "meaningful vote" on the final Brexit deal, a Downing Street spokesman said: "We have been pretty clear in the Commons that we will bring forward a motion on a final agreement that will be approved by both Houses before it is concluded.
"We expect and intend that to happen before the European Parliament debates and votes on the agreement."