For months, Theresa May has remained tight-lipped about her priorities for leaving the EU, rarely offering more insight than 'Brexit means Brexit.'

But that will all change in a landmark speech this week in which she is expected to outline that Britain will leave the single market and customs union, if that is the only way to regain control of our borders.

She risks creating a void in the Conservative party by effectively opting for a 'hard Brexit', which many senior figures, including Tories, fear will be detrimental to the economy.

in a landmark speech this week, Theresa May is expected to outline that Britain will leave the single market and customs union

It will also come as a blow to other countries on the continent after the EU's chief Brexit negotiator, Michel Barnier, admitted earlier this week that a 'special relationship' was needed with London in order to maintain financial stability for other bloc members.

Mrs May is expected to declare 'We're on our way out' as she starts the process of removing the country from the European Court, as well as the single market and customs union, in a triple departure.

She will attempt to pursue a way of staying the single market while still wiping out freedom of movement during what will inevitably be a long, drawn out negotiation process - but will make it clear that the latter is more important to her.

According to the Sun, she will also say: 'The overwhelming majority of people — however they voted — say we need to get on and make Brexit happen.

'Business isn't calling to reverse the result but planning to make a success of it. And the House of Commons has voted overwhelmingly for us to get on with it too.'

Brexiteers (left) will be delighted at the speech, but she risks creating a void in the Conservative party by effectively opting for a 'hard Brexit', which many senior figures, including Tories (pro-EU campaigners pictured right), fear will be detrimental to the economy

By doing so, she is putting faith in her peers to strike up successful free trade deals with other countries around the world.

It comes as a strident Brexiteer tipped as the leading candidate to become Donald Trump's new ambassador to the EU claimed America can become Britain’s ‘rich uncle’ during Brexit negotiations.

Professor Ted Malloch, who was interviewed by the President-elect's transition team at Trump Tower earlier this month, said if he gets the job he will advise the billionaire businessman to offer the UK a 'game-changing' trade deal with America.

In regard to her speech, a senior source told the Sunday Telegraph: 'She's gone for the full works. People will know when she said "Brexit means Brexit", she really meant it.'

Professor Ted Malloch said if he gets the job as ambassador he will advise the billionaire businessman to offer the UK a 'game-changing' trade deal with America

If the Supreme Court rules against the Government tomorrow and forces the PM to get Parliamentary permission before triggering Article 50, as it is expected to, Mrs May will also pledge to publish a bill immediately.

Downing Street is prepared for the pound's value to drop further, as it has done with all previous indications of a hard Brexit.

But despite immigration being the key factor in the Leave camp's historic victory back in July, a YouGov poll today found that more than half of Brexiteers are not prepared to take a financial hit in exchange for tighter immigration laws.

Nicky Morgan, who has endured a turbulent relationship with Theresa May of late, told The Sunday Times: ''Leave voters were told they could have immigration control and economic prosperity, and the onus is on the Government to deliver that for them.

'That means aiming high in the negotiations, putting maximum participation in the single market at the heart of their strategy, not treating economic policy as an afterthought.'