London Mayor Ken Livingstone says Heathrow should not get a third runway.

Mr Livingstone came out against the extra runway during Mayor's question time on Wednesday, saying carbon emission fears meant all airport expansion needed to be reconsidered.

"Our increasing knowledge about the threat from climate change means that policies on airport expansion now need to be re-evaluated," Mr Livingstone said.

"I have already made clear my view that the need to reduce carbon emissions has significantly undermined the case for increasing the capacity of airports in the southeast.

"I do not think there is a case for a further runway at Heathrow.

"Carbon emissions from London's airports need to be tackled as part of an international response to climate change.

"Heathrow is a major international aviation hub and plays a role in serving the aviation needs of Europe as a whole and not just London or the UK.

"From a global standpoint, the problem with carbon emissions is not so much their current levels, but their predicted growth and the lack of technological progress towards cleaner-fuelled aircraft."

He said the business trips were not an issue but the massive growth of short-haul holidays should be halted by slapping environment levies on those travelers.

"The bulk of growth in aviation travel from the UK has been in short-haul leisure trips," Mr Livingstone said.

"A policy for reducing carbon emissions from aviation in the UK must ensure that offsetting the full environmental damage of such carbon emissions is included in the price of tickets, which will lead to reduced demand for these trips.

"Growth in business trips has been much smaller and could be sustained as part as an overall policy to stabilize aviation emissions."