David Cameron has told ITV News he had always intended to publish a draft bill on the EU referendum.
He told Political Editor Tom Bradby in Boston: "In an interview a few weeks ago, I said I was interested in doing anything and everything to strengthen and give extra credibility to the pledge of a referendum in the next Parliament before 2017.
"Obviously, publishing a Bill, which we can show to the British people, we can show to parliament and campaign for, is a very sensible way of adding strength to the pledge that I have made...I have intended to publish this Bill all along.
"People need to know this is a serious pledge that they can bank. So seeing a Bill, a Bill that will put in place that referendum is part of adding to the strength of this pledge."