Theresa May will trigger the UK's exit from the EU next Wednesday

Britain will begin Brexit by triggering Article 50 of the EU's Lisbon Treaty on March 29, Prime Minister Theresa May's spokesman has confirmed.

Britain's envoy to Brussels Tim Barrow "has informed the EU this morning that Britain will trigger Article 50 on March 29," the spokesman said.

Brexit Secretary David Davis said in a statement that the UK is "on the threshold of the most important negotiation" for a generation.

Monday's announcement means that May will meet her self-imposed deadline of the end of March to get the withdrawal process underway.

She was cleared to take the step when the European Union (Notification of Withdrawal) Act gained royal assent last week, after a Supreme Court ruling forced her to seek the approval of both Houses of Parliament.

Ms May will address MPs in a statement to the House of Commons following her regular weekly session of prime minister's questions on March 29.

European Commission said the European Union is fully prepared for Brexit negotiations.

"Everything is ready on this side," Margaritis Schinas, the spokesman for European Commission chief Jean-Claude Juncker, told a briefing. "We are ready to begin negotiations."