UK Prime Minister Theresa May is expected to announce she is willing to take the UK out of the single market, the customs union and the European Court of Justice.

May is to outline her strategy for leaving the European Union in a major speech on Tuesday (17 January), in which it is anticipated she will stick to her 'Brexit means Brexit' promise and is prepared for the UK to leave the single market in order to take control of UK borders.

The prime minister is to make it clear the two issues she is not prepared to negotiate on are immigration and reclaiming UK sovereignty, with the EU having stated access to the single market comes with accepting freedom of movement.

May is also set to issue a plea during her speech - referred to as the Plan for Britain - for people from the 'leave' and 'remain' camps to set aside their differences and work together for the country's future.

"One of the reasons that Britain's democracy has been such a success for so many years is that the strength of our identity as one nation, the respect we show to one another as fellow citizens, and the importance we attach to our institutions means that when a vote has been held we all respect the result," she is expected to say, according to the Press Association.

"The victors have the responsibility to act magnanimously. The losers have the responsibility to respect the legitimacy of the result. And the country comes together.

"Now we need to put an end to the division and the language associated with it - Leaver and Remainer and all the accompanying insults - and unite to make a success of Brexit and build a truly global Britain."

Although those within the Remain camp have strongly warned against severing trade links with the EU, The Sun reported May was not prepared to negotiate on free movement to remain in the single market.

A senior government source told the newspaper: "The EU is demanding a high ransom to remain in the single market — the continuation of free movement. The PM is quite clear she is not prepared to accept that.

Theresa May
British Prime Minister Theresa May leaves 10, Downing Street, London Daniel Leal-Olivas/Getty Images

"It's looking increasingly likely we'll leave the customs union too because membership would forbid us from holding bilateral trade talks with any other country. That would negate the whole purpose of leaving the EU."

However, the news of May's intention to announce she is prepared to leave the single market has been met with concern in some corners.

"Theresa May has had six months to give some clarity, she hasn't done it. She needs to do that on Tuesday and she needs to reassure the country, Shadow Minister for Brexit Kier Starmer said in an interview with Sky News.

"If, as is expected, she says that she will be leading the UK out of the single market the question is, 'What are you going to put in its place? What are you going to negotiate to make sure that business can succeed in the future in the way it succeeds now?'"

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.