Brexit bill to get royal assent on Thurs

Royal assent on the Brexit bill is expected on Thursday, Brexit Secretary David Davis says.

Britain's Prime Minister will notify parliament later this month when she has triggered Article 50. (AAP)

Legislation empowering Prime Minister Theresa May to trigger formal negotiations on Britain leaving the European Union is expected to receive royal assent on Thursday, Brexit Secretary David Davis says.

Davis, who steered the Brexit bill through parliament, did not say when May planned to trigger Article 50 of the Lisbon Treaty, which allows a nation to leave the EU after up to two years of negotiations.

Since Britain voted to leave the EU in a referendum in June, the government has not assessed the potential impact of failing to agree a deal on Brexit, Davis told members of a parliamentary committee on Brexit.

Leaving the EU without a deal is "not as frightening as some people think, but it's not as simple as some people think," he said.

Speaking to parliament on Tuesday, May said the triggering of Article 50, which she has promised to do by the end of this month, will be "a defining moment for our whole country."

The Article 50 bill passed both houses of parliament late Monday following six weeks of debate.

Royal assent is a formality of approval by Queen Elizabeth II for all legislation before it is enacted.