Mr Miliband said Labour would reverse the coalition's cut in the top rate of tax from 50p to 45p "if there was an election tomorrow".
"Next April David Cameron will be writing a cheque to each and every millionaire in Britain for £40,000," he said.
"If I was in government tomorrow one change I would make in relation to the better off - first change in a Labour budget - we wouldn't be cutting the top rate of income tax from 50 to 45p.
"If there was an election tomorrow that is what we would do."
The Labour leader said borrowing was going up under the coalition and the money was being used to "keep people idle".
He told the Andrew Marr Show: "Yes, there would be cuts if we were in government but if you make the pace of those cuts slower, if you take less money out of the economy now it would be better for the economy, better for growth."
He added: "Two and a half years ago the jury was out, the jury can now return its verdict because it hasn't worked, what this Government has done.
"The borrowing in the first five months of this year is 20% higher than it was last year."
Mr Miliband said a tax on bankers' bonuses would raised £2 billion, which could be used for housing and jobs for young people.
"Our answer is not, as this Government is doing, borrowing to keep people idle. Let's get people back to work."
Mr Miliband promised that shadow chancellor Ed Balls would be "iron" in his resistance to irresponsible spending commitments.
"There will be tough decisions that we'll have to make as a government," he said.
Under him, a Labour government would be "different from the last and previous Labour government" because "we are not going to have lots of money to spend".
There would be "tough settlements right across our public services", he warned.
The Opposition leader said: "What we are going to see from the Labour Party this week, talking about how we can change the way the energy companies work, how we can change the pension system so people get a fairer deal, how we can change the banks ... that is all about how in tough fiscal times, when there isn't money around, Labour can make a difference.
"We are not going to spend money that we don't have, of course we're not. One of the things about Ed is that he is going to be iron in saying you cannot make commitments, both he and I are absolutely clear about this, you cannot make commitments unless we have an absolutely clear idea where the money is coming from."
Setting out the "predistribution" economic theory, Mr Miliband said it was about "higher pay over time" - potentially including for public servants.
He said: "Of course it's about higher pay over time ... it could be in the public sector."
Mr Miliband has given banks an ultimatum that they need to have successfully separated their investment arms from their retail operations before a Labour government comes to power or face a new law to force their break-up.
"What I want is a country where a small business or an individual going into their High Street bank knows that bank is working for them not gambling their money on the international markets," he said.
The Vickers Commission's banking reforms had been "watered down" over a separation, he said, and could require new laws to enforce the split.
Mr Miliband said: "It's a very clear message I have for the banks: either they sort it out themselves so that once and for all the High Street bank is not an arm of the casino operation, or the next Labour government will, by law, split those banks up so that once again we return to the best traditions of British banking."
The Labour leader dismissed concerns that banks would relocate abroad to avoid a split.