Theresa May will formally begin the Brexit process by the end of March 2017, she has told the BBC.
The prime minister confirmed the deadline for triggering Article 50 of the Lisbon Treaty, which sets in place a two-year process of withdrawal.
She has also promised a “Great Repeal Bill” in the next Queen’s Speech, which will overturn the act that took the UK into the EU.
It will remove the European Communities Act 1972 from the statute book.
The government will also enshrine all existing EU law into British law.
It comes as the Conservatives gather for their annual conference.
The repeal of the 1972 Act will not take effect until the UK leaves the EU under Article 50.
In an 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.”
Conservative Party chairman Patrick McLaughlin told BBC Breakfast this proved the party was “very serious” about starting the process of leaving the EU, but added negotiations would not be conducted in the public eye.
“You don’t say exactly what you are going to negotiate on, but once negotiations are concluded we will say what we’ve achieved and how we’ve achieved it,” he said.
“To give a running commentary on every last sentence and paragraph would be ridiculous.”
Mrs May has also made clear she does not want the conference, being held in Birmingham, to be dominated by the issue of leaving the EU.
Tory MPs are divided between favouring a “hard Brexit” outside the European single market to obtain complete control over immigration, or a “soft Brexit” where the UK remains in the free trade zone, but potentially has to comply with some EU rules.
“I’m clear that we are not going to be completely consumed by Brexit,” Mrs May told the Sun on Sunday.
“What I want to deliver is real change. To build a country that works for everyone.”
Labour MP Phil Wilson, from the Open Britain campaign, said businesses want the prime minister to commit to single market membership.
“We still know nothing about the government’s plans for our new relationship with the EU, whether over trade, security or migration,” he said.
“As car manufacturers have made clear, it is essential that the UK remains a member of the single market to protect investment and jobs.”