People wanting to offset the carbon emissions produced when they go on holiday will be able to judge suppliers on a new government code of conduct published today.
Environment secretary David Miliband said he hoped the new voluntary standard and code of practice would "raise the bar" for the industry.
Carbon offsetting is where individuals and organisations invest in projects that cut the amount of carbon dioxide in the atmosphere, to offset the emissions caused by driving to work or taking holidays.
It has become increasingly popular, but campaigners are sceptical about its benefits. Friends of the Earth director Tony Juniper warned today: "Carbon offsetting schemes are being used as a smokescreen to avoid real measures to tackle climate change."
Tony Blair came under fire last week when he announced he would not give up long-haul flights and exotic holidays, but would instead offset all his private trips abroad. The government already offsets all official travel, and hopes to be carbon neutral by 2012.
Launching the new code of practice today, Mr Miliband acknowledged carbon offsetting was "not the answer to climate change".
But he said that where some emissions "can't or won't be avoided", it had a role to play. Today's guidelines, which have now been put out for consultation, would help ensure that this measure was as effective as possible.
"People need to be sure that the way they offset is actually making a difference," he said.
"The government's standard and code of practice, with a quality mark so people can check easily before they choose an offsetting product, will help to provide that certainty."
There have been concerns about some carbon offsetting projects, particularly those which involve planting trees, and today's guidelines suggest providers stick to trying to cut emissions in developing countries through energy efficiency and renewable technologies.
Currently only four providers - PURE the Clean Planet Trust, Global Cool, Equiclimate and Carbon Offsets Ltd - meet the government's standard but others, including lastminute.com and First Choice Holidays, have agreed to meet it by the end of the year.
However, Mr Juniper warned: "We urgently need to cut our emissions, but offsetting schemes encourage individuals, businesses and governments to avoid action and carry on polluting."
He added: "Carbon offsetting should be a measure of last resort, after steps have been taken to cut emissions. The government has a role to play in ensuring that offsetting schemes are genuine. But its main role must be to ensure that UK emissions are cut."
Simon Retallack, head of climate change at the IPPR think tank, welcomed the new standards but said: "Today's improvement in offsetting should not be interpreted as a green light for a business-as-usual approach to flying.
"Companies and passengers should also take steps to reduce the number of flights taken, and the government should reassess its policy on airport expansion to reduce the number of flights in the future."