"Let's fight this together," Cameron said as he defended a series of draft proposals put forward by the European Council president yesterday that have angered eurosceptics from his own Conservative Party.
"I do believe that with these draft texts... Britain is getting closer to the decision point," he said in a parliamentary debate on the issue.
Cameron did not give a timing for the referendum but, asked about June 23 -- which has been mooted in British newspaper reports --he said the date would not be too soon after regional elections planned for May 5.
He faced criticism from leading eurosceptic MPs including John Redwood and Bill Cash, as well as London mayor Boris Johnson -- a political ally who has expressed doubt on the proposals from Brussels.
Also Read
"We've got a lot more to do on this," Johnson told SkyNews ahead of the debate
"The prime minister is making the best of a bad job. Let's wait and see when this whole thing is agreed and try and see what it really means. Every bit of it," he said.
"I believe we are making real progress in all four areas, but the process is far from over. There are details still to be pinned down," he added.
"The question is not could Britain succeed outside the European Union. It's how we would be most successful," he said.