The approval gives Prime Minister Theresa May the power to start the formal process of leaving the European Union.
Britain edged closer to leaving the European Union after parliament passed a bill that will give Prime Minister Theresa May the power to initiate the long exit process.
The 'Brexit Bill' was approved by both the upper and lower houses of parliament and after securing symbolic approval from Queen Elizabeth, which could come early on Tuesday, May will be free to invoke Article 50 of the EU's key treaty, triggering two years of exit negotiations.
The House of Commons approved the bill weeks ago, but the 800-strong House of Lords fought to amend it, inserting a promise that EU citizens living in the UK will be allowed to remain after Britain pulls out of the bloc.
They also added a demand that parliament get a "meaningful" vote on the final deal between Britain and the remaining 27 EU nations.
Both amendments were rejected by the Commons, where May's Conservatives have a majority.
"We have been clear that the prime minister will trigger Article 50 by the end of March," her spokesperson said
Break up of United Kingdom?
But in a blow to May's government, the prospect of Scotland's exit from the United Kingdom suddenly appeared a realistic possibility as well.
Hours before the Brexit vote, Scottish First Minister Nicola Sturgeon called for a referendum on independence within two years to stop Scotland being dragged out of the EU against its will.
In an announcement that took many London politicians by surprise, Sturgeon vowed that Scotland would not be "taken down a path that we do not want to go down without a choice."
The European Commission, however, quickly responded saying that Scotland would have to reapply to join the EU rather than inheriting Britain's membership.
But Sturgeon's call pushes to centre stage one of the prime minister's biggest concerns about Brexit — that it could lead to the break-up of the United Kingdom — as she prepares to fire the starting gun.
Irish republican party, Sinn Fein, also called for a swift referendum on Northern Ireland leaving the UK and joining the Republic of Ireland.
And Welsh nationalists Plaid Cymru said Sturgeon's announcement meant the time had come for a national debate about Wales' future.