Sources have told FarmOnline that Mr Tuckey threatened the spill if party leader Malcolm Turnbull's preference to support the amended legislation won the day.

However, reports indicate that the spill move has failed to gain enough support for a vote against Mr Turnbull to go ahead.

The Coalition has been arguing the merits of the legislation since 10am, with only a break for Question Time.

During that period the chances of the Coalition agreeing to the deal on offer from the Labor Government have plummeted as the extent of backbench anger has become increasingly apparent.

At lunch sources indicated a two-thirds majority were in favour of the amended ETS; that has now slipped to 50:50.

Sources say the atmosphere within the meeting has become increasingly hostile, with all members opening up on what they really think of the situation.

Notably, influential figures who have a keen eye for the detail of the legislation, have told the meeting that the amendments would cost the taxpayer an extra $7 billion and not deliver any extra reduction in carbon emissions.

Among those speaking against the package was Andrew Robb, who is currently on sick leave but was previously the Opposition's climate change spokesman.

Sources say Mr Robb spoke passionately for 10 minutes arguing the package was "not good enough" and should be rejected.

The scenario is disastrous for both the Coalition and Mr Turnbull's leadership.

It is now apparent that Mr Turnbull does not have the level of partyroom support that he previously thought, and that the Coalition is hopelessly divided on the issue.

In a cruel twist, if the partyroom meeting is completed, Mr Turnbull is scheduled to host Christmas drinks for the Parliamentary Press Gallery journalists this evening.