Reflecting on the budget, Miliband said the government was "shrugging their shoulders" at the prospect of five more years of austerity and said the prime minister was making a big mistake by supporting continued austerity.
"The Tories have resigned themselves now to a lost decade," the Labour leader said in an interview with The Times. "George Osborne is saying there is going to be another five years of low growth and borrowing, with living standards being squeezed. The danger is that people become despairing, that they think there is no change that is possible.
"At the next election, the biggest opponent will be the sense that no one can sort out this problem. Our challenge is not to let people succumb to fatalism and think nothing can be done."
The Labour leader's comments come as ratings agency Fitch said it was putting the UK on "rating watch negative" because of rising debt and stagnant growth, which raises the prospect that it too, like Moody's, could downgrade the UK from AAA status.
"We should be investing in infrastructure and housing ... [The Tories] are borrowing more because of a lack of growth. Borrowing would be lower if you followed the right economic strategy ... if you have a failing economic strategy, you just don't say I am going to plough on regardless," he said.
Miliband said he was prepared to pay a mansion tax on his house, believed to be worth at least £2m. "The difference between Cameron and me is that he's cutting taxes for himself, I might be raising them for myself.
"You've got food banks all around the country. These are dire circumstances for a lot of people. The notion that it's right to take money off the poorest people but the rich can't get by is just wrong."
As well as looking at the status of non-domiciles, the Labour leader said he also wanted to name and shame companies that paid too little tax.
Miliband was also unwilling to commit to matching the government's spending plans. "I can't make spending decisions without knowing the economic circumstances of 2015," he said.
On Saturday, Miliband will speak to the Labour party's people's forum in Bimingham. He will also accuse the chancellor of missing a chance to change course in the budget, which signalled more spending cuts and tax rises after 2015. Instead he will set out the Labour policies he claims will pull the UK back, including a 10p rate of income tax funded by a mansion tax and using money raised from the 4G mobile phone licences sale to build new homes.
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