The government, due to unveil its plans for reform in the Queen's speech next week, insists it is not necessary to put the issue to the people. But it is already facing signs of a revolt by Tory backbenchers either opposed to the reform itself or to any further constitutional reform proposed by the Liberal Democrats.
The Labour leader said: "We had a very clear manifesto position, which was for a referendum, a 100% wholly elected second chamber and proper codification of powers. That is the way I think about this issue.
"As the person who helped write the manifesto I have always thought the referendum is a good idea, since if you are making such a large constitutional change I don't see how you can justify not having a referendum."
Miliband said he was not playing games to undermine the government. "On this issue I am pro-reform. I do want to see reform of the Lords. There are some people who don't, but I don't think I should be nominating the people who make our laws.
"We have got lots of fantastic Labour peers who help make our laws but I hold to the elective principle. That is the best system we have."
He denied that a referendum would be a delaying tactic, saying: "It helps you win legislative consent. What has bedevilled this issue is that it gets gummed up in parliament.
"I am sure we can win a referendum. We have got all three party leaders saying they want change, and I cannot see how this could not be won."
Miliband dismissed suggestions that there was no need to have a referendum since it had been in all three parties' manifestos. "I am sure for some people House of Lords reform was uppermost in their mind at the time of the election, but I don't think that applies to the majority. I don't think it was the decisive issue at the general election and therefore I think it is quite hard to argue against a referendum."
Asked whether he was prepared to impose a three-line whip in the Commons, Miliband said: "We have got a manifesto position on this and I am giving you a sense of where we are coming from."
