British lawmakers have backed a bill authorizing the start of European Union exit talks, voting by a decisive 498 to 114 to push the measure past its first major legislative hurdle.

During two days of debate in the House of Commons, many legislators from both government and opposition said they would respect voters' June 23 decision to leave the EU and back the bill.

But pro-EU members of Parliament from opposition parties will try to insert more amendments at the next stage of the process, seeking to prevent an economy-shocking "hard Brexit."

The Conservative government wants to have the bill approved by early March so it can meet a self-imposed March 31 deadline for triggering two years of EU divorce talks.