New figures reveal the Federal Government's revised mining tax will collect $60 billion less revenue over 10 years than the original proposed tax.

Freedom of Information documents released by Treasury show the original super profits tax would have made $99 billion in revenue over a decade.

This compares with the revised Minerals Resources Rent Tax which is forecast to earn $38.5 billion over the same period.

The Government says it has always been upfront that its revised mining tax will generate significantly less revenue than the original proposed tax.

The Greens say they will put more pressure on the Government to reinstate its original mining tax proposal.

Greens Leader Bob Brown says the Government gave away billions to mining companies.

"It's very alarming. These figures show that the Federal Government is going to forgo $60 billion in tax revenue with its new deal with the miners," he said.

"That's $60 billion that Australian taxpayers won't see."

Treasurer Wayne Swan has defended the amount of revenue the revised tax will generate, saying 10-year projections are highly variable.

"We said it would raise significantly less revenue than the previous proposal. We said it at the time, the revenue that still flows from the MRRT is still strong, it's still important," he said.

But Opposition resources spokesman Ian MacFarlane says the latest figures damage the Government's argument for the tax.

"It highlights that this whole tax has been poorly thought through. The estimates are rubbery and the Government really has got no idea on what sort of income it's going to get, particularly in the out years," he said.

Prime Minister Julia Gillard says she will not revert to the first mining tax.

"We will deliver through the Australian Parliament the tax as I agreed it with Australia's biggest mining companies," she said.

"We will not be compromising that agreement in order to secure the legislation through."