Key Points:

New Zealand's poor record of growing greenhouse gas emissions has been exposed internationally, just as the incoming National-led Government goes back to the drawing board to decide how to reduce emissions.

The UN Climate Change Secretariat in Oslo released figures on Monday showing the growth in New Zealand's emissions between 1990 and 2006 to be among the worst in the world's industrialised nations.

It ranked countries according to the percentage change in emissions - measured in millions of tonnes of carbon dioxide equivalent - and only five countries fared worse than New Zealand.

They were Turkey, Spain, Portugal, Australia and Greece.

Emissions remain a hot political issue following the election and National's support agreement with Act threatens to send the country's response virtually back to square one.

Labour passed an emissions trading scheme into law earlier this year to put a price on carbon and to try to reduce emissions.

National and Act are now going to set up a select committee to examine - among other things - whether a carbon tax is a better option.

A carbon tax was vehemently opposed by National and Act when put forward by Labour but incoming Prime Minister John Key yesterday had a softer view.

"It will, at the insistence of Act and we're not opposed to doing this, look at whether there is an alternative," Mr Key told Federated Farmers in his first speaking engagement since winning the election.

"There's an argument that says [a carbon tax] is more predictable for a period of time until an emissions trading scheme works, and it might be a transitional mechanism - or it might be that in the end, industry having had a look at it decides it's a better idea."

Asked later whether a carbon tax was back on the table as an option, Mr Key said it was.

"I'm just simply saying, we're putting all things on the table," he said.

"One is potentially a carbon tax, something that the Act Party has supported pretty heavily - the second is a reformed emissions trading scheme."

National campaigned on having an emissions trading scheme, but one that would be reworked.

Act campaigned on scrapping the emissions trading scheme altogether.

Mr Key said National had campaigned strongly on its position but if there was a strong argument that could be put up on a carbon tax "then we'd look at that".

He wanted the select committee process and new legislation completed before the end of 2009 - and preferably no later than the end of September.

The process is likely to rekindle memories of the divisive "fart tax" campaign by farmers in 2003 which culminated in National MP Shane Ardern driving a tractor up Parliament's steps.

In 2005 National launched a campaign against Labour's proposed carbon tax and even had a website dedicated to axing it.

The irony of National's now considering it was not lost on Greens co-leader Jeanette Fitzsimons yesterday.

"A number of people who totally opposed it when it was Green Party policy and then later when it became Labour Government policy are now advocating it," she said. "You kind of have to ask, well where were they when it was on the table?"

The Greens have previously suggested using a carbon tax as a transition measure through to an emissions trading scheme.

Outgoing Climate Change Minister David Parker slated National's move and suggested the "dithering" over what to do would mean a loss of investment and jobs.

"Clearly this is just an exercise in dragging the chain for as long as possible," Mr Parker said.