British lawmakers are pressuring the government to give them a say on negotiating terms for the U.K.'s exit from the European Union.

They have called a debate in Parliament on Wednesday on an opposition motion calling for lawmakers "properly to scrutinize" Britain's position.

Prime Minister Theresa May has said she will trigger two years of official exit talks with the EU by March 31.

Opposition lawmakers — and some from May's Conservative Party — say Parliament should be given a say first. They worry the government has decided to seek a "hard Brexit," which means leaving the bloc's single market.

In a bid to head off a Conservative revolt, May has promised that lawmakers will get a say, as long as it "does not undermine the negotiating position of the government."