''The policy I am supporting today is the same policy I supported as John Howard's environment minister,'' he told Parliament.

''We as Liberals believed in the superior efficiency of the free market to set a price on carbon.''

He said Mr Rudd's scheme was very similar to the former Howard governments' approach, especially after amendments agreed to with the Liberal party last year. It appropriately balanced environmental effectiveness and economic responsibility.

Mr Turnbull, who was given extra time by Labor to speak on the matter, said the emissions trading scheme was the ''only policy on offer that credibly allows us to cut emissions by 5 per cent by 2020'', with the flexibility of larger increases.

However, Mr Turnbull lost the leadership of his party over the issue and his successor Tony Abbott has vowed the Coalition will not introduce an emissions trading scheme or carbon tax. He revealed recently his party's policy of direction action, which includes an emissions reduction fund to provide direct incentives to industry and farmers to reduce carbon emissions.

Mr Turnbull said politicians were obliged to future generations, to make sure that they made the country a better place, as well as their parties.

''We are already experiencing the symptoms of climate change,'' he said.

Opposition Leader Tony Abbott said this morning that he had talked to Mr Turnbull about the matter, but would not divulge the contents of those conversations. He would prefer people did not cross the floor, but would not prevent Mr Turnbull from doing so.

It comes as a new Fairfax Nielsen poll shows 45 per cent of people preferred Mr Abbott's fund and 39 per cent backed Labor's trading scheme. However, more people preferred Mr Rudd's broad approaches to climate change (43 per cent) to Mr Abbott's approach (30 per cent).

It also found Labor holds a solid 54-46 lead over the Coalition on a two-party preferred basis, but Mr Rudd's lead as preferred prime minister fell. Fifty eight per cent prefer Mr Rudd, down 9 points, and 31 per cent prefer Mr Abbott, up 10 points.