The $11-billion Mineral Resource Rental Tax (MRRT) was passed Wednesday morning because of the Labor government's $100 million pay-off deal with the Greens.

However, the details of the deal will remain a secret until the Treasury releases economic reports and assessments on the last week of November. Greens Leader Bob Brown disclosed they inked a confidentiality agreement with Labor. Negotiations were made behind closed doors.

"The government has agreed to an additional revenue measure at least equivalent to the $20 million a year ($100 million over five years) lost from raising the mining tax threshold to $75 million," Mr Brown said in a statement.

The Greens previously pushed for a reduction in fuel rebates and the establishment of research funding for the mining industry.

The agreement is in response to the Greens demand for fresh negotiations on the MRRT after the government hiked the tax threshold to secure the support of independent MP Andrew Wilkie.

Opposition Resources spokesman Ian Macfarlane said the secret deal is a cause of concern. He said Labor inking secret agreements with other parties is not the way to run Australia.

Treasurer Wayne Swan, who described the agreement with the Greens as reasonable, said it was victory for the public.

"But this isn't so much a win for the government as it is for the Australian people and for the cause of economic reform amid an ocean of negativity and fear from (Opposition Leader Tony Abbott) and a handful of vested interests," News.com.au quoted Mr. Swan.

"The MRRT will help us lock in the benefits of the boom and help those parts of our economy that aren't in the mining boom fast-lane," he added.