Chancellor George Osborne dismissed Labour's tax plans as a "con" which would see state inspectors assessing people's homes.
Labour leader Ed Miliband last week announced proposals to bring back the 10p lower rate of income tax which was scrapped by Gordon Brown, funded by a levy on homes worth more than £2 million.
But Mr Osborne said the coalition Government's policy of raising the income tax threshold was a fairer way of helping the low paid and claimed Labour's "mansion tax" would end up being extended to more modest properties.
He told ITV's The Agenda: "It's very costly to implement. It means you have to send inspectors round the country valuing all the homes - not just the homes worth over £2 million but those worth less."
The Chancellor said there were not enough "mansions" to cover the cost of a tax cut for millions of people. "So either it's a tax con and the money comes from somewhere else or it's soon a homes tax and they say it's a mansion tax before the election and then very quickly (it) becomes a homes tax on many people who are not living in mansions at all."
Mr Osborne claimed that "the inspectors get their foot in the door" and then "after the election suddenly it's everyone's homes that are potentially a target and Labour will have created a new tax". The Chancellor added: "It's just another thing that proves that I don't think they understand aspiration in this country."
Mr Osborne acknowledged that the rich should be expected to pay more, but fairness in the tax system also meant allowing working people to "get on".
He said: "In a time like this you expect the rich to pay more and actually we are forcing the rich to pay more and indeed cracking down on those who don't pay their taxes but fairness is also about having a system where people who work hard and get on can get on in our society, fairness is about a welfare system that doesn't pay for people to stay at home. Fairness is quite a broad concept and people feel the system's unfair but I don't think this kind of tax con is a solution to that."
Deputy Prime Minister Nick Clegg, whose Liberal Democrats back a mansion tax, also rejected Mr Miliband's proposals as a "pale imitation" of his own party's policies.
Mr Miliband hopes to split the coalition with a Commons vote forcing the Lib Dems to choose between backing a mansion tax or maintaining unity with the Tories.