Britain's upper house of parliament will consider any changes made to proposed Brexit laws on Wednesday evening, shortly after they have been voted upon by the lower house of parliament, the opposition Labour Party said.

Prime Minister Theresa May faces a showdown with rebels in her Conservative Party on Wednesday after refusing to accept demands for parliament to have a "meaningful vote" on Brexit that could stop Britain crashing out of the European Union with no deal.

The debate in the lower chamber will start sometime after 1200 GMT. Labour said the upper chamber would then consider any changes at around 1830 GMT.