The PM will today give details of the EU proposals to MPs as he tries to convince eurosceptics its a good deal for Britain.
The Prime Minister will set out details of the deal hammered out with Brussels, a draft of which was published on Tuesday morning, in the House of Commons this afternoon.
Mr Cameron claimed the measures he has negotiated delivered “substantial change” but he is facing significant criticism that he has not met his Conservative Manifesto pledges and even that the migrant welfare changes are “unworkable”.
Senior Conservative Liam Fox has claimed that up to five members of the Cabinet are ready to campaign for Brexit.
The proposed deal will see an “emergency brake” on EU migrants receiving in-work benefits – but it is far short of the four-year ban on in-work payouts the Prime Minister had promised.
In addition, the brake will not be in place until 18 months after a referendum and EU workers in the UK will get “graduated” in-work benefits.
Child benefit will continue to be paid to EU migrants working in the UK who have children living in Europe – but it will be linked to the standard of living in that country. Mr Cameron said the practise would stop entirely.
There are concerns at the Department of Work and Pensions over whether there is a system that can cope with 28 levels of child benefit and administer graded tax credit payments.
Senior Government officials have even suggested it may not be something that can even be delivered.
Mr Cameron is also under pressure to allow Cabinet members who want to campaign for Brexit to start speaking out against membership of the EU now.
The Prime Minister has said they are not permitted to take sides until after the 18-19 February summit where EU leaders will finalise the terms of the deal.
Mr Cameron received a major boost when Theresa May – who those from the ‘leave’ campaign were hoping would back their drive – appeared to signal her support for the “stay” campaign.
However, Dr Fox, a staunch eurosceptic who has been sharply critical of the proposals, told the Radio 4 Today programme: “I think there will be a number of Cabinet ministers with a range of different responsibilities who will want to be in the Leave camp.”
He added: “I don’t know exactly how many, but I can think of four or five for certain.”
Boris Johnson, who is only in the political cabinet, so not bound by Mr Cameron’s gag, said on Tuesday that there was “much, much more that needs to be done” for a proper EU deal.
He also expressed doubts about the “red card” system that allows a group of 15 EU countries to block legislative proposals.
There was also some disquiet in the City over the “emergency brake” system that will allow Britain to “raise concerns” over legislation tailored for the eurozone, which does not amount to the veto many had hoped for.
Mr Cameron will also begin his campaign to win over European leaders, especially those in eastern Europe who have been opposed to the benefit changes.
The Prime Minister has admitted there is more work to be done on the detail of the eventual deal and European Council President Donald Tusk said it was a “good basis for a compromise”.
Foreign Secretary Philip Hammond said the Government was not expecting a “significant negative reaction” to the plan which Downing Street says has allowed Mr Cameron to fulfil several manifesto commitments.
The deal includes an emergency brake proposal which would allow countries to stop paying in-work benefits if public services are being overwhelmed by economic migration.
It also offers protections for non-eurozone states and a legally binding assurance that the UK is not expected to take part in “ever closer union” in the bloc.
The reform plan received widespread condemnation from those campaigning to leave the EU, including former defence secretary Liam Fox and UKIP leader Nigel Farage.