Labour leader Ed Miliband told protesters at a mass rally today that he was proud to stand with them as huge numbers of people demonstrated against spending cuts.
Mr Miliband told the TUC rally in London's Hyde Park that the Government was wrong to make such deep cuts in public services.
He was heckled by a small number of protesters when he said that "some cuts" were needed, but most people applauded his speech.
The Labour leader did not join a march through central London but did address the rally.
"The Tories said I shouldn't come to speak here today but I am proud to stand with you.
"People are here from all walks of life and different backgrounds, speaking for mainstream Britain"
Mr Miliband said: "Our struggle is to fight to preserve, protect and defend the best of the services we cherish because they represent the best of the country we love.
"We know what the government will say: that this is a march of the minority. They are so wrong. David Cameron: you wanted to create the big society - this is the big society.
"The big society united against what your government is doing to our country. We stand today not as the minority, but as the voice of the mainstream majority in this country.
"The midwives from Kingston here to speak up for maternity services.
"The sure start workers from Hampshire here to speak up for children's centres. The small business owners from Liverpool here to speak up for jobs. The teachers and students here to speak up for the next generation.
"Every one of us knows that today the country faces difficult times. But we know too there is a different way. We hold to some simple truths: We need jobs to cut the deficit. Unemployment is never a price worth paying. The next generation should never have their hopes sacrificed on the altar of dogmatic deficit reduction.
"There is a need for difficult choices, and some cuts. But, this government is going too far and too fast and destroying the fabric of our communities."
Mr Miliband said the hundreds of thousands of people on the march rejected the Government's "politics of division", adding: "It falls to us to be the unifiers of our country.
"That is why it is so important that this is a peaceful protest that wins public support. A protest remembered for its cause and for its purpose.
"And it falls to us to be the optimists too. We do need to cut the deficit. But we must also protect families struggling to get by. We must also protect the promise of Britain that the next generation does better than the last.
"We must also preserve the things we value in our communities: the library, the citizen's advice bureaux, the community centre. We know, from generations before us, that it is not just politicians who make change happen, it is people."
Len McCluskey, general secretary of Unite, told the protesters they were bearing witness to services closing, old people going without care, libraries, swimming pools and parks going to "ruin" and young people heading for a life on the dole.
"But you represent a spirit of resistance in every workplace and community that says we are not going to have our way of life killed so that the rich and greedy can live as they please."
Mr McCluskey said that every time Deputy Prime Minister Nick Clegg stepped out of doors it cost police £2 million to protect him, adding: "We cannot afford that any more - if you were to go on a national tour we'd be bankrupt."
The unite leader attacked the Government's "assault" on the NHS, warning ministers that privatising the health service would spark the same protests as those against the poll tax when Margaret Thatcher was Prime Minister.
He also urged Labour MPs to hold the Government to account rather than simply waiting for the next general election.
Brendan Barber, general secretary of the TUC, told the rally that today was just the beginning of the campaign.
"We will fight the Government's brutal cuts in our workplaces and our communities.
"Today we are speaking for the people of Britain, and David Cameron, if you want to meet the Big Society - we're here in Hyde Park. It's time you started listening."
Michael Leahy, general secretary of Community Union and TUC president, said: "Today is a great day of unity and solidarity. People have come from all over the UK with one simple message for Osborne, Clegg and Cameron: There is an alternative.
"Today has also brought back many painful memories for me - it reminds me of the eighties. The Tories have resurrected TINA - there is no alternative.
"But I fear it's not just TINA that is back from the 80s. It's the same old Tories - who still think unemployment is a price worth paying. That price was 18 years of misery and hardship wreaked on working people."
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