Existing workers' rights will be guaranteed after Britain leaves the European Union, prime minister Theresa May as she took the unusual step of addressing delegates on the first day of her party's conference.

Amid pressure to spell out what Brexit could look like after Britain voted to leave the European Union on June 23, Mrs May announced a new bill which would convert European Union law into British law. The 'Great Repeal Bill' would give business and workers maximum certainty, she said.

Mrs May was given a standing ovation as she appeared on the stage in Birmingham, and she said the referendum result was 'clear', 'legitimate' and the 'biggest vote for change this country has ever known'.

She also defended her predecessor's decision to call the European Union referendum, saying that there was 'no finer accolade than to say David Cameron put his trust in the British people'.

But amid speculation about whether Britain would attempt to remain in the single market, she reiterated her determination not to give a 'running commentary or a blow-by-blow account of the negotiations', adding that 'history is littered with negotiations that failed when the interlocutors predicted the outcome in detail and in advance'.

While she said there would be 'no sudden and unilateral withdrawal', she said Article 50, the process for leaving the European Union, would be invoked 'no later than the end of March next year'.