In a speech to unveil the manifesto in Edgbaston, Birmingham, Mr Brown said Labour was facing "the fight of our lives" adding: "The future will be progressive or Conservative but it will not be both.
"We are in the future business, we are building a future fair for all."
He dismissed "empty slogans about change" from the Conservatives and pledged a "realistic and radical plan for Britain".
He said he wanted to create a "bigger middle class than ever before" and, in the wake of the expenses scandal, pledged to replace "discredited and distrusted politics with one where you, the people, are the boss".
He pledged to spread excellence across public services - with every hospital a foundation trust, more power and responsibility for "strong school leaders" and for underperforming police forces to be taken over and chief constables replaced.
"Labour will be restless and relentless reformers. Reformers of the market and reformers of the state," Mr Brown said.
Cabinet minister Lord Mandelson described it as a "Blair plus" manifesto and denied Mr Brown had had to be converted to his predecessor's public service reforms: "He invented New Labour with Tony Blair and myself and others."
Among Labour's manifesto commitments are not to raise income tax rates in the next Parliament, and not to extend VAT to items like food and children's clothes.
Asked for a firmer commitment to rule out a rise in VAT, Mr Brown said: "We have not raised VAT since 1997, the only party that has raised VAT in the last 25 years is the Conservative Party."
In a few weeks' time the manifesto will either be a reminder of promises of a better future that you can try to hold Mr Brown to or a memento of ideas that the country has rejected
BBC political editor Nick Robinson said the manifesto specified the need for "tough choices" but did not appear to give much detail about them.
But Mr Brown said: "We've done more than any other country to set out our plans in detail, the tax changes, the public spending reductions and the growth we will achieve to make that possible."
The prime minister later told Channel Four that he was prepared to take "tough decisions", and that Labour had a deficit reduction plan in place.
Labour promised not to raise income tax in its 2005 manifesto, but went on to introduce a new 50p tax rate for incomes over £150,000.
Mr Brown said he had not wanted to take that measure, but "had to" because of the banking crisis and had decided that those with the "broadest shoulders" should bear the biggest burden.
Other pledges in the manifesto include a right to recall MPs, a referendum on changing the voting system and on removing the last hereditary peers from the House of Lords, and a free vote in Parliament on lowering the voting age to 16.
They are doing it again. If they haven't managed to do it in 13 years, why would anyone believe they are going to do it this time?
Labour is also proposing to extend paternity leave with a "father's month" of four weeks' paid leave.
It also promises a new toddler tax credit of £4-a-week from 2012 for families with young children who earn less than £50,000.
The manifesto also pledges patients in England will get a one-week guarantee to get results from a test for cancer.
There were further pledges to push for an international bank levy and work guarantees for the long-term unemployed.
Royal Mail plans
Mr Brown also said he had been personally affected by the Fiona Pilkington case - the woman who killed herself and her daughter after years of bullying from local youths.
He said he wanted a Britain where anti-social behaviour and crime were "dealt with quickly" and those who did not get redress would be able to take out an injunction at the expense of their local authority.
Business Secretary Lord Mandelson denied that Labour had dropped its commitment to part-privatise Royal Mail, plans which were unpopular with some Labour backbenchers and the postal workers' union.
They've had 13 years... there's no real change there
Tory leader David Cameron
The manifesto says "for the future, continuing modernisation and investment will be needed by the Royal Mail in the public sector".
Lord Mandelson told BBC Radio 4's World at One programme: "We are not resiling from the legislation that we introduced originally." He said it had been shelved because of "market conditions" and they could return to it if they changed.
Mr Cameron said Labour's manifesto contained nothing new.
"They've had 13 years...there's no real change there," he told a rally in Loughborough.
The Tory leader added that Labour was in "desperation", and its campaign was "all about fear, it's all about frightening people".
Shadow education secretary Michael Gove admitted "there were a few good ideas" in the Labour manifesto, but added that they were all taken from the Tories.
Lib Dem leader Nick Clegg said Labour had promised "fairness and new politics" in 1997, 2001 and 2005: "They are doing it again. If they haven't managed to do it in 13 years, why would anyone believe they are going to do it this time?"
On the election trail at the Vauxhall Astra factory in Ellesmere Port, Cheshire, Mr Brown refused to be drawn on the news that the three Labour MPs accused of fiddling their expenses are to get legal aid to help fund their defence.
Mr Cameron had earlier said it was "a complete outrage", and pledged that if the Conservatives come to power, future MPs would not be eligible for legal aid under such circumstances.
The Conservatives will unveil their manifesto on Tuesday, the Lib Dems on Wednesday.
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