Triggering Article 50 of the EU’s Lisbon Treaty, the formal procedure for leaving the bloc, will open a two-year timetable for difficult negotiations, meaning Britain could be out of the EU by 2019.
“The UK’s permanent representative to the EU informed the office of (European Union President) Donald Tusk that it’s the UK’s intention to trigger Article 50 on March 29,” Prime Minister Theresa May’s spokesman told reporters.
The spokesman said May would notify Tusk in writing and then give a speech to the British parliament.
“We want negotiations to start promptly,” he said.
Britain voted in a June referendum by a 52 percent majority to leave the EU — the first member state ever to do so.
Monday’s announcement comes just days before the European Union celebrates the 60th anniversary of the Treaty of Rome which created the bloc.
The European Commission, whose chief negotiator Michel Barnier will spearhead the talks with London on behalf of the other 27 member states, said it was ready for the Brexit process.
“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,” he said.
Britain’s Brexit minister David Davis said in a statement that Britons had approved a “historic decision” to leave the EU after four decades of membership.
“Next Wednesday, the government will deliver on that decision and formally start the process by triggering Article 50,” he said.
“We are on the threshold of the most important negotiation for this country for a generation.”
May has said she wants to leave the European single market in order to be able to control immigration.
The European Commission is expected to provide an initial answer to Britain’s Article 50 notification within 48 hours but negotiations are not expected to start for several weeks or even months.
The British government has insisted the Brexit process is irreversible once Article 50 is triggered, although experts have said there is no legal ban on member states changing their minds before they have actually left the European Union.
May’s preparations for Brexit have been hit by Scottish First Minister Nicola Sturgeon’s announcement last week that she planned a new independence referendum in order to keep EU ties.
Irish nationalist party Sinn Fein in Northern Ireland, which made major gains in regional elections earlier this month, has also called for a referendum on breaking off from the United Kingdom and uniting with the Republic of Ireland.
Of the United Kingdom’s four nations, Scotland and Northern Ireland voted to stay in the EU in the June 23 vote while England and Wales voted to leave.
May on Monday began a tour of Wales, Scotland and Northern Ireland aimed at boosting support for Brexit.