Britain's Prime Minister Theresa May leaves 10 Downing Street in central London, Britain, September 14, 2016. [Photo/Agencies]

UK Prime Minister Theresa May said she will start the formal process of leaving the European Union by the end of March next year, ending uncertainty surrounding the UK exit process by setting a date to invoke Article 50.

Under the EU accession treaty, originally signed in 1972, the UK will have two years from formally tell the EU that it is leaving the organisation.

May, speaking to the BBC ahead of her ruling Conservative Party's annual conference, said she intended bringing in an act of parliament that would enshrine existing EU laws in British law; this would allow a smooth transition and permit parliament, at a later date, to repeal those EU-based laws which it does not want, including freedom of movement.

She told the BBC: "I want to give a greater degree of clarity about the timetable we are following."

Britons voted to leave the EU in a June referendum this year, causing the resignation of David Cameron as prime minister and May's installation in his place.

"This is about delivering for the British people, and this is not just about leaving the EU, it's about that essential trust people have in their politicians. The people have spoken, and we will deliver on that," she said.

May was at pains to stress that British workers' rights, as laid down in EU law, would continue unaffected because of the all-embracing act of parliament that would be introduced at the end of the two-year mandatory exit period.

That was seen as a direct rebuttal of the opposition Labour Party's position, which was that workers' rights would be endangered.

May indicated she was keen to seek a negotiated relationship with the EU on departure, including trade, rather than the "hard exit" with no deal favoured by some so-called Brexiteers in her party, which would leave the UK with no formal relationship with the EU.

Her decision means the UK will have formally left the EU before the next general election, in May 2020.

"We'll be an independent country. Crucially, we still do want to have a good relationship with Europe and the European Union," she said.

After leaving the EU, the UK will be free to strike a direct trade deal with China, something both Beijing and London have said is a priority.

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