Shadow cabinet on Monday will discuss tactics for the house vote. But emissions spokesman Ian Macfarlane yesterday confirmed the vote against. If the vote had been taken during the last sitting, as the Opposition wanted, the Coalition would have opposed the bills.

Although there would be an argument for not opposing in the house on "good faith" grounds during the negotiations, a vote against would prevent the split in Coalition ranks being put on show before the legislation gets to the Senate, where the detailed amendments would be moved if a Government-Opposition deal was reached.

The Government Senate leader, Chris Evans, yesterday wrote to parties and independent Senator Nick Xenophon saying the Government would largely dedicate the next sitting fortnight to the legislation, extending Senate hours if necessary. The bills will arrive in the Senate by Tuesday. The Government wanted to ensure the legislation was voted on this year, the letter said. Family First's Steve Fielding said he opposed an extension of hours, because the vote should be delayed until after Copenhagen.

As talks between Climate Minister Penny Wong and Mr Macfarlane continued yesterday, the Nationals leader in the Senate, Barnaby Joyce, said a petition against the legislation he had organised had attracted 5000 signatures so far.

Senator Joyce, who has campaigned relentlessly against the scheme, said if there was a difference with the Liberals, it should not be allowed to split the Coalition.

"That would be a terrible outcome and a ridiculous outcome," he told Sky News.

"You'd have to be out of your tree to suggest something like that," he said. The coalition was a vital mechanism to have a conservative opposition to deal with the Labor Government.

"If someone wants to suggest that [breaking the coalition], well, it just goes to show how completely politically naive they are."