Senator Brown yesterday outlined the essentials any emissions trading system must have to win the support of his party, which holds five of the critical seven balance of power votes in the Senate.

"The penalty clause for us not acting is almost unthinkable," he said.

"This planet, this country, is on the verge of cataclysmic times, such as the human collective experience has never known.

"I'm not talking here as a green politician. I am talking on the basis of the experience, the study, and the dire warnings from the world's best thinkers."

Senator Brown told the National Press Club yesterday that unless the scheme began in 2010 and produced real cuts in greenhouse pollution levels by 2015 it would not do enough to prevent dangerous levels of climate change.

The Greens are opposed to any compensation going to energy companies, he said.

"Did we compensate the asbestos industry? No, the money has gone to the victims," he said.

"Why should the money [from the sale of permits] go to the big polluting industries and the loggers? The market should be their destiny."

The Greens want all the money raised from the sale of greenhouse permits to go towards helping people use less energy in their lives.

They are calling for investment in renewable energy and public transport, and the retrofitting of houses with insulation and solar hot water systems.

By 2020, emissions should be 40pc below their 1990 levels, Senator Brown said, and 90pc lower by 2050.

The Government is yet to reveal its 2020 greenhouse reduction target, although it has already committed to reducing emissions by 60pc by 2050.

But Senator Brown indicated the Greens would not reject the emissions trading system outright if it did not at first appear to live up to their expectations.

Instead, Senator Brown said, he was prepared to support the Government if it was prepared to consider other environmental initiatives such as a boosted renewable energy target and feed-in laws which pay people with solar panels for any energy they generate but do not use.

The Government's climate change adviser, Ross Garnaut, last week outlined his vision for an emissions trading scheme, saying it could begin in 2010 although that would require a tough timetable.

The Government will release a green paper containing the options for the emissions trading system next week.

Draft legislation is expected at the end of the year.