Ed Miliband today pledged to push through his controversial reforms to Labour's links with the unions, saying that the "bigger risk" was to keep things as they are.
Miliband told the TUC congress that it would be a "massive challenge" to implement his planned reforms.
"Of course, it is a massive challenge. It will be a massive challenge for the Labour Party to reach out to your members in a way that we have not done for many years and persuade them to be part of what we do. And like anything that is hard it is a risk. But the bigger risk is just saying let’s do it as we have always done it," he said.
Miliband's proposals were mostly received in silence by delegates, without the boos or heckles that some had predicted.
While Miliband's reforms have been badly received by some union leaders, union members are thought to be more receptive.
A recent YouGov poll revealed that 60% of trade union members affiliated to Labour believe Mliband's reforms are "sensible." However, the poll also revealed that most of those are not supporters of the party.
Miliband pledged to push on with his reforms, insisting they are necessary to stop union members being affiliated to Labour "in name only".
"Some people ask: what’s wrong with the current system? Let me tell them: we have three million working men and women affiliated to our party. But the vast majority play no role in our party. They are affiliated in name only. That wasn’t the vision of the founders of our party. I don’t think it’s your vision either. And it’s certainly not my vision," he said.
Miliband said his plan to allow union members to "opt in" to the party could more than double its membership.
"This is an historic opportunity to begin bringing people back into the decisions which affect their lives. It means we could become a Labour party not of 200,000 people, but 500,000, or many more. A party rooted in every kind of workplace in the country, a party rooted in every community in the country, a genuine living, breathing movement."
One delegate was roundly cheered by the congress after asking Miliband: "Can we get a clear answer? Are you for or against austerity?"
Miliband refused to make any promises to limit future spending cuts.
"I am not going to pretend there are easy choices for the next Labour government. There will be a deficit we will have to reduce. We are going to have strict spending limits. The easy thing for me is to come along and make a whole set of promises and then afterwards you say you have not keep your promises. We have to be credible and get the deficit down," he said.
Miliband also promised to clamp down on zero-hours contracts and accused David Cameron of oozing contempt for ordinary workers
"We have a prime minister who writes you and your members off. Who doesn't just write you off, but oozes contempt for you from every pore. What does he say about you? He says your members are a 'threat to our economy'. Back to the enemy within."
He compared Cameron to failed US presidential candidate Mitt Romney, who was recorded saying that he didn't worry about 47% of voters.
"We know from recent experience what happens to political leaders who write off whole sections of a country," Miliband added.
"That's what Mitt Romney did when he talked about the 47% of people who would never vote for him. And look what happened to him. Friends, my job is to make sure that's what happens to David Cameron as well."
Reactions from union leaders were mixed. The general Secretary of Unite Len McCluskey broadly welcomed the speech, describing it as the work of "a real leader".
Others were less convinced. Dave Prentis of Unison said he would not take steps to help Labour to recruit more members, and called on Miliband to think again.
"He talks about having the courage to change but I was always told if something ain't broke, why fix it?" he said.