Show courage and back changes, Ed Miliband tells unions
Ed Miliband has urged unions to have "the courage to change", as he attempts to persuade them to back an overhaul of the way Labour is funded.
Several unions have attacked the Labour leader over his plans to remove the automatic payment of fees by millions of their members to the party.
But Mr Miliband told the TUC that this "historic" change would strengthen his chances at the general election.
He also predicted Labour's membership could swell to more than 500,000.
Mr Miliband and several union leaders have disagreed during this week's annual TUC meeting in Bournemouth about his plans to change the way the party's funding works.
However BBC political correspondent Chris Mason said the speech was not a "leadership defining bust-up with the unions", with Mr Miliband stressing areas of agreement - such as living standards, zero hour contracts and wages.
The Labour leader wants to abolish the automatic affiliation fee paid each year by about three million union members to Labour.
Instead he proposes giving people the choice of "opting in" - becoming full Labour members - when they join a Labour-supporting union.
Mr Miliband acknowledges this will cost money, but argues it will expand his party and increase activism.
One union leader accused him of "living in cloud cuckoo land", while others have also voiced concerns.
But Labour front bencher Chuka Umunna told BBC Radio 4's The World at One the party was willing to risk financial harm "because it's the right thing to do".
The proposed changes follow a row over allegations that the Unite union tried to rig the Labour choice of a candidate for the Falkirk seat at the next general election. An investigation by Labour has found no evidence of wrongdoing, emboldening his critics.
Ahead of his speech, Mr Miliband told ITV's Daybreak "we are going to get these changes through", adding that Labour's internal structures were "old-fashioned" and had to change.
Labour MP John McDonnell said the row had bolstered the power of the unions who now had six months to make demands of the party.
In his speech, delivered to a subdued audience, Mr Miliband said: "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.
"That's why I want to make each and every affiliated trade union member a real part of their local party, making a real choice to be a part of our party so they can have a real voice in it."
Mr Miliband added: "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."
The Labour leader called his plan a "massive challenge" but said: "It is you who have been telling me year after year about a politics that is detached from the lives of working people. We need to build a party truly rooted in the lives of all the working people of Britain once more.
During his speech, Mr Miliband attacked the Conservatives, accusing David Cameron of showing "contempt" for working people.
He said: "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'.
"Six and a half million people in Britain who teach our children, who look after the sick, who care for the elderly, who build our homes, who keep our shops open morning, noon and night. They're not the enemy within. They're the people who make Britain what it is.
"How dare he? How dare he insult people, members of trades unions as he does? How dare he write off whole sections of our society?"
Mr Miliband repeated the slogan he first used at last year's Labour conference, of his party being the UK's "one nation party".
But he faces a difficult task to persuade leaders of several of the major unions that his proposed changes are justified.
Paul Kenny of the GMB - which has cut its funding for the party by £1.2m a year - mocked the plans as looking as if they had been made up "after a night out".
Unite general secretary Len McCluskey warned at fringe meeting: "Our Labour leadership has to start demonstrating they are on the side of ordinary working people."
But Dave Prentis of Unison said the squabbling and "infighting" had to stop, or people would not vote Labour in 2015.
And the TUC general secretary, Frances O'Grady, used her speech to the Congress on Monday to ask union activists to "roll up their sleeves" and influence Labour's policies, while opposing the Conservatives.
Conservative Party chairman Grant Shapps said: "Instead of taking on the unions, Ed Miliband has buckled under pressure. He's backed down over Falkirk, backed down over serious reforms to the union link.
'While Ed Miliband is spending his time trying to soothe his biggest paymasters, we're dealing with the deficit, controlling immigration and fixing the welfare system to help hardworking people."