Dr James Tansey, chief executive of Offsetters, whom the Vancouver Organising Committee appointed as the first Official Carbon Offset Supplier to an Olympic Games, told insidethegames that he found it hard to understand why London 2012 dropped the idea of carbon neutrality.

"I think London 2012 got it right in terms of building smart, green buildings from the start in the Olympic Park," he said.

"They were model buildings - wonderful examples of design.

"But the London Organising Committee stepped away from the concept of carbon neutrality.

"I don't fully understand what happened there.

"I think there was pressure on the Olympics from the Government."

The London 2012 velodrome was a model of green construction - but the Games themselves fell short of the announced ambition to be carbon-neutral

As the name of the company he co-founded implies, Tansey – a Professor at the University of British Colombia – is committed to the idea of enabling companies and corporations who build up greenhouse gas emissions in building projects or transport to recompense the global environment by funding green projects around the world such as wind farms or forest protection projects.

But he acknowledges that not everyone is sold on the idea.

"There's still a discussion around offsets," he said.

"For whatever reason, some people credibility issues with offsets.

"Some people's attitude to offsetting indirect carbon footprints is: you shouldn't have flown in those planes in the first place.

"But people are eager to fly to the Olympics fly anyway.

The Closing Ceremony of the 2010 Vancouver Paralympics, which with the Olympics were the first carbon neutral Games

"The business model for offsetting is pretty well established now. 

"People were worried that it would prove to be too expensive.

"But it's about two to three per cent extra on a ticket price to make a Games carbon neutral.

"In the past, Games have added green projects as an afterthought, and by the time they come round to doing anything they have already constructed their buildings, and it is very hard to integrate green ideas.

"It is much cheaper and more efficient if you integrate We believe it should be a requirement in the Bid book for cities to show what they are doing with regard to the carbon footprint of their proposed Games."

In 2010, the London Olympic Authority announced plans to make the London 2012 Games the "Greenest Olympics Ever" by ensuring that they were fully sustainable and carbon neutral.

But two years later the emphasis had shifted, and the talk was of "reducing" and "mitigating" the carbon footprint of the Games.

London 2012 announced: "Our first objective is to get a handle on our climate impact and then work out how to avoid our emissions.

Carbon offsetting - that is, funding environmental projects around the world to offset the emissions from transport and building projects - would have been one of the prime means of reaching a carbon neutral Games.

But in the run-up to London 2012 this practice was criticised by environmental groups who saw it as encouraging developed nations to do whatever they wanted without trying hard to reduce their emissions in the first place.

A spokesman for Friends of the Earth described offsetting as "a false solution," adding: "The focus needs to be on emissions reduction, both in the UK and abroad, rather than playing one country off against another."