The speech is expected to focus heavily on the economy and immigration, two of the key issues for voter in June’s EU referendum.
Mrs May is expected to claim that while Britain would ideally like to retain single market access, she will not hesitate to walk away from the UK’s European Economic Area membership if Brussels bureaucrats try to frustrate the Government’s attempts to reclaim control of Britain’s borders.
This move is designed to give Mrs May’s Brexit strategy a clearer definition and looks set to frustrate many Remain supporters, who are desperate for Britain to retain access to the single market.
A source told the Telegraph: “It’s going to be incredibly significant.
“It will cover everything from the single market to immigration. It will be substantial.”
The unidentified minister said: “She needs to make clear that Britain is prepared to leave the single market or they [the European Union] will try to screw us down.
David Davis (L) and Boris Johnson (2nd L) are reportedly having a significant input in the speech
“Britain can always say we would like access to the single market but not full membership.”
The speech is set be delivered after the Supreme Court ruling which will decide whether she has to formally consult Parliament before triggering Article 50.