UK Prime Minister Theresa May is to deliver her long-awaited speech on Brexit on Tuesday 17 January, according to a Number 10 source.

The address will come on the same day MEPs are expected to elect the EU Parliament's new president, with Martin Schulz quitting the post to run for the Social Democratic Party in Germany's general election.

The details of May's major speech are not yet known, but the Conservative premier has hinted that the UK will no longer have full access to the EU's single-market as the government seeks immigration curbs.

The prime minister also promised that her ministers will have a "comprehensive, wide-ranging plan" to split from the EU.

"A plan to build a country where wealth and opportunity are shared; where all of us, no matter what our background, play by the same rules; and where future generations enjoy the same opportunities from which their parents have benefited throughout their lives," May said on 9 January.

"I will say more about this plan in the coming weeks. I will talk more about our plans for economic reform, our plans to build a Global Britain and our ambitions to build a more united country."

The UK government will be in negotiations with the EU once Article 50 is invoked. But May and her ministers are still waiting for a final ruling from the Supreme Court, which will decide whether MPs must vote on the issue.

MPs are expected to vote through a draft Article 50 legislation in the House of Commons, but the bill could be held up in the House of Lords where Labour and the Liberal Democrats have more than 330 peers.

The EU Commission's chief Brexit negotiator, Michel Barnier, revealed in December that he expects a deal between the parties to be completed in October 2018 and ratified before March 2019. The exit talks can last two years once May has invoked Article 50.