The Labor Party has indicated it would wind back any deal the Federal Government struck with the crossbench to reduce the Renewable Energy Target, as hopes of a bipartisan deal fade.

The target is for 20 per cent of Australia's energy mix to come from renewable sources, like wind and solar, by 2020.

But with falling energy demand and emissions intensive industries paying big power bills, the Coalition wants to cut the target.

Labor has agreed to negotiate a lower figure but is at odds with the Coalition over how big any cut should be, and its environment spokesman Mark Butler has indicated the Opposition would tear up any deal struck with the crossbench if it wins power.

The 20 per cent figure represents 41,000 gigawatt hours (GWh).

Industry Minister Ian Macfarlane last week revealed his final offer was a target of 32,000 GWh but Labor wanted a figure in the mid-to-high 30,000s and maintained there would be no deal if the Government did not lift its number.

Not reaching a deal and passing corresponding legislation this week will have expensive consequences.

Analysts said the renewable energy certificates market will collapse back to where it was before the negotiations between Labor and the Coalition started if a deal is not reached soon, and unions fear jobs will go in the aluminium sector.

Both the Government and the Opposition have agreed to exempt the energy-intensive aluminium industry from the scheme but the concession will not go ahead unless an agreement is reached.

The Australian Aluminium Council said that would force it to pay between $50 million and $80 million if the relevant legislation was not passed by March 31.

Faced with the prospect of not securing a deal with Labor by that deadline, Environment Minister Greg Hunt has resumed talks with the crossbench.

But the Clean Energy Council, which represents the renewable energy industry, said it needs certainty and will take no comfort from a deal between the Government and the crossbench.

It wants a bipartisan deal, arguing that without it the industry could face more upheaval if the Government loses the next election.

Labor reserves right to lift target: Butler

Today Mr Butler confirmed those fears, saying Labor reserved the right to lift the target if it won office.

"We'll be taking very ambitious policy around renewable energy to the 2016 election, but we don't know yet what possible deal the Government might be talking about to the crossbench," he said.

"We'll wait and see that, but we obviously reserve our position to continue to lift the level of ambition on renewable energy, far beyond what Tony Abbott has in mind.

"We obviously would like the ambition to be lifted and we would want to see whether there was a prospect of lifting the target, so not creating investor uncertainty, lifting opportunities for investment into the future."

The Government would need the support of six of the eight senate crossbenchers to change the legislation if it cannot reach a deal with Labor.

Palmer United Party senator Dio Wang supports the current target of 41,000 GWh but said he would consider backing a lower figure if it had bipartisan support, given the industry's need for certainty.

A spokesman for Motoring Enthusiast Senator Ricky Muir said he has not seen a final proposal but was hoping for bipartisan support.

A spokesman for Independent senator Jacqui Lambie said she wants an exemption for all emissions intensive industries in Tasmania, but will support lowering the target to 32,000 GWh.

Family First senator Bob Day said he will support the Government's push for a lower target but could also back keeping the 41,000 GWh target in place if hydro power was included in the scheme.

Fellow senate crossbencher David Leyonhjelm is set to meet the Government this afternoon.