Farming organisations have expressed caution over government targets that aim to slash UK greenhouse gas emissions by 80% in the next 40 years.

A report by the government's climate change committee said the "challenging but feasible" cut could be achieved at a cost of 1-2% of GDP by 2050.

The committee, which is overseeing the new Climate Change Bill, told Climate Change Secretary Ed Miliband in a letter that it was vital to act on emissions to avoid "catastrophic consequences".

The committee's Adair Turner wrote: "Climate change poses a huge potential threat to human welfare... that is why it is so vital that a global deal is reached on climate change and that the UK contributes significantly towards this.

"But we have the potential to reduce our emissions by 80% or more by using energy far more efficiently, by investing in developing new energy sources and by making relatively minor lifestyle changes."

However, the Climate Change Task Force, made up of organisations including the Country Land and Business Association and the NFU, said the report had not recognised farming emissions were different from energy and industry sectors.

Farming emissions could not be reduced as dramatically as in other sectors, it said.

As there were uncertainties about the effects of non-greenhouse gases produced by farming, the government needed to take a careful approach when allocating emission production targets.

The industry was well-placed to reduce its carbon footprint but it could only achieve "modest cuts" in methane and nitrous oxide emissions, the task force added.