The Government has told MPs that voting against the repeal bill would result in the UK suffering a “chaotic” exit from the European Union.
Asked whether the Government was confident of the outcome, the PM’s spokesman said: “Yes. We’ve said this is a hugely important bill in terms of preparing the way for a smooth Brexit for business and the rest of the country, and we encourage all MPs to support it.”
The second reading vote is expected either on Monday evening or in the early hours of Tuesday.
The bill overturns the 1972 Act which took Britain into the European Economic Community. In doing so, it incorporates EU laws onto the UK statute book.
Labour will vote against the legislation, mainly because it objects to so-called Henry VIII powers, which are named after a statutory instrument used by the Tudor king to force through new laws without full parliamentary scrutiny.
Labour says these powers in the bill amount to a “power grab”, but the party has rejected accusations it is trying to derail the Brexit process.
Speaking to Sky News, shadow Brexit minister Jenny Chapman said: “Labour will not block Brexit.
“If you disagree with anything the Government does on Brexit, you are a Brexit betrayer.
“Our position is about this being a very bad bill – it’s bad for our democracy, it doesn’t enable Parliament to take back control the way that people want, and crucially it gives ministers these powers that they just don’t need for Brexit.”
However, about a dozen Labour MPs from Leave-backing constituencies could rebel against Jeremy Corbyn’s orders.
Mrs May, whose majority in the Commons relies on a deal with the DUP after the Conservatives’ poor showing at the last General Election, also faces a potential rebellion.
Several Tory MPs have said they are unhappy with the bill, with former attorney general Dominic Grieve describing it as “an astonishing monstrosity”.
They are expected to vote for it for now and seek amendments in the future, which could leave the minority Government having to make concessions to avoid defeat.
The Government has rejected any suggestion of a “power grab”. It said the bill is necessary to ensure stability and continuity to businesses and citizens when Britain’s EU membership ends in March 2019.
Ahead of the debate, Brexit Secretary David Davis said: “A vote against this bill is a vote for a chaotic exit from the European Union.
“Without it, we would be approaching a cliff edge of uncertainty which is not in the interest of anyone.”