In an email to party activists last night he wrote:
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.
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.