The UN's top climate change official said on Thursday that record oil prices, which have surged to $146 a barrel, were positive for the environment.

"I think they are a net positive. First of all you see that through decreasing demand in Europe and North America where people are becoming much more conscious of petrol prices," Yvo de Boer told AFP.

"High oil prices also improve the competitiveness of renewable sources of energy and make it more interesting to focus on energy efficiency," he added.

De Boer, who heads the United Nations Framework Convention on Climate Change (UNFCCC), noted however that high prices also made heavy forms of crude oil, which take energy-intensive extracting and refining, more attractive.

"There is a risk that as dirty forms of oil become commercially more attractive that would lead to an increase in emissions," he said.

One such worry is the Canadian tar sands, a dense mixture of sand, water and petroleum used to extract bitumen, which are controversial because of the environmental impact of extracting and refining the mixture.

Experts say the tar sands are only viable if world oil prices remain high.

There has been a surge in interest for the resources, however, given the possibility of a major source of oil from a stable country such as Canada.

The head of India's state oil company said on Thursday that India could invest up to $10-billion in the tar sands in the future.

AFP