The SNP have said that they will try to force the Prime Minister to appear before MPs as Mr Cameron is set to lay out his specific demands to the President of the European Council Donald Tusk in a letter this week.
Top of the list of seven demands will be that EU citzens will have to wait four years to claim benefits. He will also insist that the goal of “closer union” for all members is dropped.
It comes amid growing concerns over the lack of clarity about the renegotiation ahead of the referendum.
In his speech, to accompany the release of the letter, Mr Cameron will seek to turn up the pressure on EU leaders while demonstrating to sceptical Tory MPs he is prepared to walk away if he is not able to get the changes he wants.
“If we can’t reach such an agreement, and if Britain’s concerns were to be met with a deaf ear, which I do not believe will happen, then we will have to think again about whether this European Union is right for us. As I have said before - I rule nothing out,” he will say.
The Prime Minister will insist he has “every confidence” that it is possible for the negotiations to deliver an agreement which works both for Britain and its EU partners.
“If and when we do so, as I said three years ago, I will campaign to keep Britain inside a reformed European Union - campaign for it with all my heart and all my soul, because that will be unambiguously in our national interest,” he will say.
But SNP Europe spokesman in Westminster Stephen Gethins said: “David Cameron is playing a dangerous game by recklessly flirting with the prospect of leaving the European Union in a desperate attempt to keep his Tory backbenchers on side – it is time that he put the country before internal Tory party troubles.”