It comes as Independent Senator Nick Xenophon issued economic modelling claiming the amended scheme would blow almost a $4 billion black hole in the budget.

The Government needs at least seven of the 32 Liberal senators to support its Bills for the scheme to become law, and should easily get that number while Malcolm Turnbull remains Opposition Leader.

However, at least a dozen Liberals will cross the floor to oppose it. They and other opponents, including the Nationals, are expected to also try to delay the vote for as long as possible.

Government Leader of the House, Anthony Albanese, said he expected the Liberals would honour their agreement to put the issue to a vote in the Senate by 3.45pm and to support it. The Government would not ''guillotine'' the debate last night, but he left open the option of trying to force senators to vote if the debate was continuing at 3.45pm.

''Climate is too important to play politics with. It's more important than any individual. It's the issue for our generation, for us and for our kids. We need to take action on climate change now on the national level prior to the globe taking action at the Copenhagen conference,'' he said.

However, Labor would struggle to get the required votes in the Senate, as the cross bench opposes the legislation and is unlikely to support the Government's move. Mr Turnbull vowed last night to keep the deal.

He said Liberal Senate leader and climate change sceptic Nick Minchin, who resigned yesterday, had promised not to frustrate the passage of the legislation. However, Senator Minchin, along with several other Liberal senators, would vote against the legislation.

Meanwhile, Senator Xenophon said the economic modelling by Frontier Economics showed the amended scheme would deliver a $3.77 billion deficit, reduce net tax revenue by $11 billion, and mean gross domestic product would be $50 billion lower by 2019-20.