The opposition's proposed amendments to the ETS include an exemption from emissions for agricultural production.

Mr Turnbull reiterated the coalition's stance during a speech to delegates at the NSW Farmers Association's annual conference in Sydney on Thursday.

He said the US and European climate change legislation had excluded agricultural emissions.

"It is absurd for the Rudd government to proceed to design an emissions trading scheme which imposes heavier burdens on Australia's industry, heavier costs on Australian farmers and workers than comparable schemes do in other countries," Mr Turnbull said.

"I just say again, the recklessness with which (Prime Minister) Kevin Rudd is approaching this emissions trading scheme poses grave risks to our economy.

"I say to you as somebody who is committed to action on climate change ... that this scheme that Kevin Rudd has is seriously flawed.

"The design should not be finalised until after the Americans have completed their legislative process and after the Copenhagen summit."

Federal Agriculture Minister Tony Burke on Wednesday told the conference technology to measure emissions from farms was not yet available and a decision on whether to include agriculture in the ETS was four years away.

Mr Turnbull said Mr Burke's statement was "absolute hogwash".

Farmers had many ways of investing in the land to reduce carbon emissions, including restoring soil carbon through improved practices, removing carbon from the atmosphere and fixing it in the soil, and tree planting and revegetation, Mr Turnbull said.

"Our single greatest comparative advantage in the battle to reduce carbon dioxide emissions is our enormous land mass, 7.7 million square kilometres," he said.

After his speech, Mr Turnbull reaffirmed the opposition will vote against the ETS in its current form.

"We believe an emissions trading scheme has to be both economically responsible and environmentally effective," he told reporters.

"The Rudd government's scheme is neither..."

He said the opposition was clear about the changes to the ETS that would be needed to secure its vote.

"The Rudd government obviously has got no plans to make those changes and have said they're not even prepared to discuss them with us.

"So the scheme in its current form ... we will vote against the scheme on the 13th of August, we've always made that very clear."