Prime Minister Theresa May on Wednesday ruled out allowing lawmakers to vote on triggering the Article 50 exit clause to begin formal negotiations to leave the European Union.
But before a debate in Parliament on its role in overseeing the government's strategy, May promised that lawmakers would be able to scrutinize the terms of the so-called Brexit.
Parliament would have "every opportunity to debate this issue." She declined to say if leaving the EU single market was a "red line" in her Brexit negotiations.
She told Parliament that her aim was to retain "maximum possible access" to the single market but control the movement of EU citizens into Britain.
Labour, the largest opposition party, tabled the motion calling for May to allow Parliament to closely examine her Brexit plan before she triggers Article 50 of the EU's Lisbon Treaty, which sets the rules for a two-year negotiating process for a nation leaving the bloc.
May has said she will trigger Article 50 by the end of March.
A growing number of opposition lawmakers and some from May's ownConservative Party have urged her to provide more clarity on her plans and to allow a vote in Parliament on her Brexit policy.
A cross-party opposition motion calling for Parliament to have a "full and transparent" debate before the government begins formal negotiations was expected to win a majority late Wednesday, but the motion omits any call to allow Parliament to vote on the negotiating strategy.
Liberal Democrat leader Tim Farron said May had already "chosen a 'hard Brexit' that was never on anybody's ballot paper" in the June referendum.
May has rejected the idea that leaving the single market means a "hard" Brexit that could be more damaging to Britain's economy.
But she has declined to give details of her position, insisting she will not provide a "running commentary" on the negotiations.
"This is a government that drew up no plans for Brexit, that now has no strategy for negotiating Brexit, and offers no clarity, no transparency, and no chance of scrutiny of the process for developing a strategy," Labour leader Jeremy Corbyn said.