Lawmakers look set to approve a bill on Wednesday empowering Prime Minister Theresa May to start Brexit negotiations, in a major step toward the United Kingdom leaving the European Union.

Seven months after the historic referendum vote to leave the 28-nation bloc, the House of Commons is expected to grant its approval for May to trigger Article 50 of the EU's Lisbon Treaty.

The bill must now still pass through the House of Lords, where there may be more opposition from unelected peers less concerned about defying the majority of voters who backed Brexit.