Theresa May will formally begin the Brexit process by the end of March 2017, she has told the BBC.
The PM's announcement on triggering Article 50 of the Lisbon Treaty - which begins the formal negotiation process - means the UK looks set to leave the EU by the summer of 2019.
Mrs May also promised a bill to remove the European Communities Act 1972 from the statute book.
She said this would make the UK an "independent, sovereign nation".
The repeal of the 1972 Act will not take effect until the UK leaves the EU under Article 50.
It will be contained in a "Great Repeal Bill", promised in the next Queen's Speech, which will also enshrine all existing EU law into British law.
This will allow the government to seek to keep, amend or cancel any legislation once Brexit has been completed. The repeal bill will also end the jurisdiction of the European Court of Justice in the UK.

Brexit campaigners have been calling for Article 50 - which begins a two-year negotiation process - to be triggered as soon as possible.
Mrs May, who had previously only said she would not trigger it this year, will be making a speech on Brexit later to the Conservative conference, which is getting under way in Birmingham.
Speaking on the Andrew Marr Show, she ended speculation about the government's timetable, saying this would be done by "the first quarter of 2017".
'Not hanging around'
Mrs May said the process of leaving would be "quite complex" but said she hoped there would now be "preparatory work" with the remaining EU members so that "once the trigger comes we will have a smoother process of negotiation".
She added: "It's not just important for the UK, but important for Europe as a whole that we're able to do this in the best possible way so we have the least disruption for businesses, and when we leave the EU we have a smooth transition from the EU."
The PM also said June's vote to leave the EU was a "clear message from the British people that they want us to control movement of people coming into the UK".

BBC assistant political editor Norman Smith said Mrs May was sending out a signal to say she is "not hanging around" on Brexit.
But she had offered little more detail on the "key issues" of single market access and immigration, he added.
Former Conservative minister and Remain campaigner Anna Soubry said she was "hugely" concerned about triggering Article 50 "as early as March" before French and German elections had taken place.
Scottish First Minister Nicola Sturgeon said the "depressing" conclusion from Mrs May's interview was that government decisions were "being driven by ideology of the hard Brexiteers, rather than interests of country".

Mrs May and Brexit Secretary David Davis will give more details of the Great Repeal Bill - which Brexit campaigners have been calling for - to conference delegates later.
The move is partly designed to give certainty to businesses and protection for workers' rights that are part of EU law.
In an earlier interview with the Sunday Times, the prime minister said the repeal bill would mark "the first stage in the UK becoming a sovereign and independent country once again".
"It will return power and authority to the elected institutions of our country," she said.
"It means that the authority of EU law in Britain will end."
Transport secretary Chris Grayling - the former justice secretary who campaigned for Brexit - said it meant there would be an "evolution not a revolution" in UK law once it leaves the EU.
He gave the example of child benefit being paid to children living overseas as an example of legislation that could be scrapped, while some environmental regulations could be retained.

Mrs May and Brexit Secretary David Davis will give more details of the Great Repeal Bill - which Brexit campaigners have been calling for - to conference delegates later.
The move is partly designed to give certainty to businesses and protection for workers' rights that are part of EU law.
In an earlier interview with the Sunday Times, the prime minister said the repeal bill would mark "the first stage in the UK becoming a sovereign and independent country once again".
"It will return power and authority to the elected institutions of our country," she said.
"It means that the authority of EU law in Britain will end."
Transport secretary Chris Grayling - the former justice secretary who campaigned for Brexit - said it meant there would be an "evolution not a revolution" in UK law once it leaves the EU.
He gave the example of child benefit being paid to children living overseas as an example of legislation that could be scrapped, while some environmental regulations could be retained.
http://www.bbc.com/news/uk-politics-37532364