Legislation enshrining David Cameron's pledge of a referendum on Britain's EU membership into law is set to be backed by Tory MPs today.
The Prime Minister last night rallied his troops to "give the British people their say on Europe" by backing the private member's Bill tabled by backbencher James Wharton.
Labour and Liberal Democrat MPs are expected to stay away from Westminster for the debate, dismissing the legislation - which has only a very slim chance of becoming law - as a political stunt.
It is designed to cement the Prime Minister's promise if re-elected in 2015 to seek to renegotiate the UK's relationship with Brussels and put the resulting deal to an in/out referendum by the end of 2017.
In May, 115 of his MPs backed an amendment to the Queen's Speech criticising the failure to include a referendum bill after it was blocked from being part of the Government's legislative programme by the Liberal Democrats.
Last night there was more harmony in the ranks as Mr Cameron hosted a barbecue for Conservative MPs in the garden of 10 Downing Street as part of efforts to nurture relations with a restive parliamentary party.
In an email message to activists, he said: "Tomorrow, the Conservative Party will vote to give the British people their say on Europe.
"As I made clear in my speech on Europe earlier this year, we want an in-out referendum by the end of 2017. And tomorrow Conservative MP James Wharton will propose a Bill that would write this commitment into law.
"The Bill has my full support - and it has support from across the Parliamentary Party: ministers and backbenchers, Conservatives of all views. We are united behind it and together we will vote for it.
"The political picture here is a simple one. Conservatives want to give people a choice on Europe. Labour don't - they're refusing to back our Bill.
"For decades, politicians have denied the British people a voice on Europe. Tomorrow the Conservative Party will fight to give them one. And let us all be proud of that."
It came as Labour leader Ed Miliband came under renewed pressure to commit Labour to a public vote when one of his MPs broke ranks to call for a vote to be held even sooner than under Mr Cameron's plans.
Dudley North MP Ian Austin, a former aide to Gordon Brown, wrote in the Express and Star newspaper: "The truth is that the UK needs to decide and I would prefer it to do so more quickly. I know this isn't Labour Party policy, but my view is that we should have a referendum next year on the same day as the European elections."
Several Tory MPs posted pictures of Mr Cameron cooking on the barbecue and said the party was in "good spirits at the moment" - one, Dan Byles, also noting that his favourite beer was "on tap" at the event.