CANBERRA - Australia's government demanded on Thursday that conservative rivals stop opposing carbon trade laws, citing a heatwave searing the country's biggest cities as evidence of Australia's vulnerability to climate change.

With Australia on bushfire alert, the government said record temperatures above 40 degrees Celsius (104 Fahrenheit) across three states this week showed the need to act urgently against climate change.

November this year has seen a long and intense heatwave across much of southern and eastern Australia. The trend is absolutely clear, the climate is warming, Assistant Climate Change Minister Greg Combet told parliament.

The opposition is negotiating changes to the government's carbon trade laws, which will be voted on next week in parliament's upper house Senate, but some opposition members are not convinced that human activity is driving climate change.

Prime Minister Kevin Rudd said negotiating with the opposition was like dealing with a mediaeval court.

It is as if we are back into the trial of Galileo or something and they are simply arguing somehow that the science is fiction and that they alone, in their own prejudiced universe, occupy fact, Rudd told parliament.

The government wants carbon trading to start in July 2011, covering 75 percent of emissions in what could become the second domestic trading platform outside of Europe.

The ETS legislation was rejected by the Senate in an earlier vote this year and a second defeat would give Rudd a trigger for a snap election.

Senior conservative lawmaker Ian Macfarlane said he expected a deal with the government by next week, despite up to 30 rebel opposition MPs promising to vote against the scheme.

I'm negotiating on the basis that by the time the Senate rises at the end of next week, he (Rudd) will have what he is demanding, but it will be on our terms, Macfarlane told radio.

The government, short of a majority in the Senate, has been negotiating changes with the main conservative opposition bloc to secure seven extra votes needed to pass the carbon laws.

The government has already bowed to a key opposition demand to permanently exclude agriculture, which accounts for around 16 percent of Australian emissions, but the opposition also wants more concessions for coal miners.

The government's carbon trading plan would reduce more CO2, create more jobs and produce a budget surplus, compared with opposition plans which carry billions of dollars in fiscal and political risk, said a report by The Climate Institute.

The opposition's scheme, which seeks to increase compensation to major emitters, would result in a deficit of more than A$36 billion ($33 billion) by 2020, while the government's plans would generate a small surplus, said the report released on Thursday.

(Additional reporting by Michael Perry; Editing by Jeremy Laurence)