The announcement on a tax band scrapped by the last Labour government and a flagship Liberal Democratic aim was made during a major speech on living standards.
Taken together, more than 25 million taxpayers would benefit, Mr Miliband said.
However, opposition parties accused him of cobbling together policies overnight, after David Cameron hinted his support for a 10p tax rate at Prime Minister's Questions on Wednesday.
Labour also suffered a blow when the influential Institute for Fiscal Studies (IFS) think-tank warned there were better ways to redistribute wealth.
Critics also cried foul when the party refused to say if either policy would be included in its General Election manifesto.
Labour insists the announcements show it is on the side of working people as the Tories prepare to bring in a tax cut for millionaires this April.
The policies also move the party closer to the LibDems, ahead of potential Coalition negotiations following another hung parliament in 2015.
Homes that are worth more than £2 million would be included in the mansion tax with the money used to pay for a 10p tax band, Mr Miliband said.
His aides brushed aside questions over whether the Labour leader himself would have to pay such a tax, but insisted he would be happy to do so.
Labour was heavily criticised when it scrapped the 10p tax rate in 2007. The then chancellor, Gordon Brown, was accused of making around five million people worse off.
The LibDems last night said many of those workers now paid no tax at all thanks to rises in the personal tax allowance.
Labour's political opponents also pointed out Mr Miliband had backed the original decision to scrap the 10p tax rate.
Shadow Chancellor Ed Balls insisted both he and his party leader had tried to persuade Mr Brown not to press ahead with the plan, but were forced to defend the move under the principle of collective ministerial responsibility.
Mr Balls added: "I said at our conference a couple of years ago it was a mistake to cut the 10p rate. Gordon Brown has said that.
"When Ed Miliband and I talked when I first became shadow chancellor, we both said it was a mistake and we needed to reinstate it and put that wrong right."
Labour say a mansion tax would raise around £2 billion a year. That would fund a 10p rate on up to £1000 of taxable income.
Some 25 million basic rate payers would be up to £100 better off as a result, the source said.
LibDem Chief Secretary to the Treasury Danny Alexander said: "The two Eds are rather late to the party, wanting to cut taxes for those on low and middle incomes. After 13 years in government, the only action Ed Balls took was to raise the amount of tax those on low incomes paid by abolishing the 10p rate. It was the biggest tax mistake they ever made and it has taken them until now to realise their error.
"The best way to cut taxes for those on low incomes is take them out of tax altogether. That is why Liberal Democrats in Government are raising the personal allowance. From April, nearly 25 million people will get a further income tax cut so they will be £600 a year better off than under Labour.
"Labour had 13 years in government to make property taxes fairer by introducing the Liberal Democrat policy of a mansion tax. With the Liberal Democrats in Government, the wealthy are paying more in each year of this parliament compared to any under Labour."