The current trend for "offsetting" carbon emissions by planting trees is doing more harm to the environment than good, MPs have been told.
Carbon offsets do not cut pollution, MPs were told
The public is being "seriously misled" by companies peddling carbon offset schemes, campaigner Jutta Kill told the environmental audit committee.
The schemes did not reduce emissions and simply gave industry a "licence to pollute" elsewhere, she argued.
People should give money directly to climate charities instead, she said.
Under carbon offsetting schemes, air passengers pay to fund tree planting and other environmental projects in developing countries.
The practice has become a badge of honour for politicians on all sides - amongst others - over the past year, as they compete to prove their green credentials.
But campaigners giving evidence to the Commons environmental audit committee, chaired by Tory MP Tim Yeo, questioned the value of offsetting as a way of tackling climate change.
Jutta Kill, of the Forests and the European Union Resource Network (FERN), was the most vehement opponent of the practice, arguing it probably did more harm than good.
Carbon offsetting was "an unbelievably inefficient way of reducing emissions," she argued, and its effects were impossible to verify.
In addition, "More than half" of the money given to companies selling carbon offsets went on research and administration costs, "benefiting not the climate but the burgeoning consultancy industry".
"We believe it is worse than nothing because it creates the illusion, or the impression, in the public that action is being taken, while we are not really addressing the task at hand, significantly reducing greenhouse gas emissions," Ms Kill told MPs.
People would be better off making "straightforward donations" to climate projects through established charities.
"This is a serious issue of misleading the public, if you are not telling people that what you are buying is something that is not very viable.
"And those that have set up this offset market are fully aware of this fact," she told the committee.
Larry Lohmann, of environmental and social think tank The Corner House, argued offsets perpetuated the myth that tackling climate change was a "matter of individual choices".
"I think this is a particularly pernicious type of miseducation in the area of climate change because if there is one lesson that the scientific analysis of the climate change problem teaches us it is that systemic change is required.
"It is not a matter of individual choices within a given set of limited options," he told the MPs.
Ending the "mining and use of fossil fuels" was far more important, he argued.
"Offsets are slowing down social change of the type which is necessary in the south, in the countries in which the offset projects are actually being constructed.
"Contrary to hype, they are actually reinforcing the reliance on fossil fuels in those countries rather than trying to bridge away from that," he added.
Ruth Davis, head of climate change policy at the Royal Society for the Protection of Birds (RSPB), also questioned the value of offsets, saying the way they were being marketed was "harmful".
"Our major scepticism about the role voluntary offsets play is the overall message that is associated with them," she told the committee.
"It is very hard to convey to people that when they are buying an offset they are not actually neutralising their impact on the global environment.
"They, I think quite understandably, believe what they are doing is buying something which means they are relieved from the responsibility of further action."
Offsetting schemes also undervalued the environmental cost of carbon emissions, she argued, and companies offering them often had "very high" profit margins and did not properly explain what they were selling.
"There are many people who are buying offsets who don't understand what they are buying.
"They are not buying an emission reduction and they are not buying neutrality," she told the MPs.
It would be better to "give people an opportunity to make a contribution that would help people manage climate change either here or abroad," she added.
Brian Samuel, of the Energy Saving Trust also questioned the role of carbon offsetting, but said they could work in conjunction with other initiatives.
"We believe that once action has been taken there is a potential role for offsetting," he said.
The committee is expected to take evidence next week from companies offering carbon offsetting services.
It is also hoping to take evidence from airlines and ministers from the department for rural affairs before producing a draft report in early May.
Among other issues, it is looking at whether there should be more robust legislation of the carbon offset market, including a compulsory accreditation scheme.
It is also examining whether customers were getting enough information to make clear choices about offsetting and whether the science behind it is "sufficiently coherent".
Last month, the government announced a voluntary code of conduct for carbon offsetting schemes to bring "greater clarity" to the industry.
Launching the scheme, Environment Secretary David Miliband said offsetting "isn't the answer to climate change".
"The first step should always be to see how we can avoid and reduce emissions," he said.
But offsetting has a role because "some emissions can't or won't be avoided", he added.