British Airways has been accused of failing to properly market a scheme to "offset" emissions by planting trees.
BA says it is proud of its record
The scheme has saved just 1,600 tonnes of CO2 since September 2005, equivalent to four return flights to New York on a Boeing 777, MPs were told.
Tim Yeo, chairman of the Commons environmental audit committee, said this was "little short of scandalous".
BA admitted take-up was "disappointing" but said marketing had been put on hold after air passenger duty rises.
BA company secretary Alan Buchanan said it had been the first major airline to introduce a voluntary carbon offsetting scheme, which allows passengers to fund tree planting and other environmental projects in developing countries.
Work had begun last year to improve its "visibility", he told the committee.
But it marketing plans were put on ice after Chancellor Gordon Brown doubled air passenger duty, as it was felt customers would be less sympathetic to the scheme.
"The take-up has been disappointing and it has been largely flat throughout the period," Mr Buchanan said.
Asked specifically how much had been offset, he told MPs it was about 1,600 tonnes a year.
"I'm not sure that a lot of passengers are as keen to offset emissions as we had hoped that they might be," he said.
MPs accused BA of not being "very adventurous" in marketing the scheme, claiming passengers did not know where to look for information and check-in staff had "blank expressions" when asked about it.
Committee chairman Tim Yeo said: "It's in fact absurd really that the level of take-up is, I believe, less than a single return flight to Sydney for Britain's best-known airline... that's little short of scandalous."
Mr Buchanan responded: "It's about four return flights to New York, I think on a 777." He added that BA runs about 50 flights a week to New York.
He told MPs voluntary offsetting had a role - but only alongside other measures such as technological developments and fuel efficiency.
"The best way to achieve a proper offset is through an organised emissions trading scheme that would cover an entire flight," he said.
"Voluntary offsetting has a place in this and is a bridge towards it, but I don't think it is the absolute solution to the problem."
He also said BA had been more proactive than most airlines in getting the aviation industry involved in the EU emissions trading scheme.
But Labour MP Colin Challen accused BA of preferring to talk about emissions trading because it was a type of "holding mechanism" that some thought may never happen.
Mr Buchanan also said it was difficult to give any accurate assessment of how many people had been put off flying by the rise in air passenger duty.
He said, because of problems since December with flying time lost through thick fog, the threat of industrial action and baggage problems, he could not compare figures with last year.
Carbon offsetting schemes have been criticised by some environmental scientists because they do not reduce emissions and their effects on climate change are difficult to verify.
Last month, the government announced a voluntary code of conduct to bring "greater clarity" to the industry.
But the environmental audit committee is looking at whether there should be new laws to clean up the industry.
During an earlier evidence session, forestry campaigner Jutta Kill said offsetting was worse than doing nothing about the environment as it gave firms a licence to pollute elsewhere.
She said people concerned about the environment should give money to climate charities instead.