GOING vegetarian may not reduce your carbon footprint, a UK report has found.

The report could hinder efforts by the vegetarian movement to have meat eaters convert to vegetarianism on the grounds that their diet is better for the environment.

Commissioned by the World Wildlife Fund and carried out by Cranfield University, the study found that eating soy, chickpeas and lentils could increase the risk of overseas forests being cleared and converted to farmland to grow those crops.

It also found meat substitutes were often highly processed and that large amounts of electricity was used to create them.

University of Adelaide chair of climate change Professor Barry Brook said the study "raised good points".

"That's why we need to take account of all energy inputs," Prof Brook said.

Advocates from either side could present a biased view by "doing apples-and-oranges comparisons", Prof Brook said, so it was only fair to compare data calculated in the same way that took into account the same factors.

However, he said it was hard to believe soy shipped from around the globe produced more carbon than locally grown meat - unless the soy was grown on land cleared for that purpose.

But Vegetarian Network of Victoria president Mark Doneddu expressed scepticism over the report, saying "even the most processed plant-based foods" had a smaller carbon footprint than meat.

"Some studies exclude factors like water usage," Mr Doneddu said.

He said he hoped people would steer away from products with big food mile counts and processed foods anyway.

Meat and Livestock Australia Manager Environment and Climate Change Beverley Henry said the report showed "a simplistic approach isn't the answer".

"Efficient red meat production is actually better for the environment than some sorts of crop production," Ms Henry said.

"It's about making the best use of land for food production, not a simple approach saying one food is better for environment than another."