British Airways has unwittingly dealt a blow to prospects for a third runway at Heathrow by revealing that its aircraft caused more pollution at the airport last year, in spite of demands from the government for an improvement.
A "warts and all" environmental update from the airline revealed that four years of progress on cutting emissions ground to a halt in 2003.
BA's fleet belched more carbon dioxide and oxides of nitrogen, reversing a downward trend. Noise from its planes would also have increased were it not for the company retiring its fleet of Concordes.
The transport secretary, Alistair Darling, announced in December that he would give the green light for contentious plans to build a new landing strip at Heathrow only if nitrogen emissions were brought under control. Without an improvement, Heathrow will breach European laws on air pollution, which come into force in 2010.
Yesterday's figures were an embarrassment to BA, which has stood alongside rival airlines in lobbying vigorously for expansion at the world's busiest international airport.
Andrew Sentance, BA's head of environmental affairs, said: "One of the things about being honest in reporting is that sometimes the trends don't go exactly the way you want year-on-year."
BA's nitrogen emissions fell by 18% between 1998 and 2002, but then edged up by 4% last year. Nitrogen oxides are responsible for lung irritations and cause particular problems for asthmatics.
The airline blamed the increase on an end to a programme of retiring older, less "green" aircraft, such as Boeing 747-200s. A decline in its flying programme tailed off, as it reached the end of a restructuring embarked upon after September 11, 2001.
Chief executive Rod Eddington pointed out that road traffic causes three times as much nitrogen pollution as aircraft around Heathrow. He called on the government to improve rail links to the airport through schemes such as Crossrail - the east-west line across London - and Airtrack, which would link the airport to stations to the south and west.
"Unless we get better rail links, road will remain supreme," said Mr Eddington.
John Stewart, chairman of the Heathrow flightpath residents' group Hacan ClearSkies, said the figures showed that a third runway at the airport remained a "pipe dream".
BA's carbon dioxide emissions rose by 300,000 tonnes to 15.4m at an untimely moment. The figures emerged just days after the chancellor announced that the Department for Transport was to be included in the government's target of cutting carbon emissions by a fifth by 2010, under the Kyoto treaty.
Richard Dyer, aviation campaigner at Friends of the Earth, said: "This increase in carbon emissions flies in the face of efforts of other sectors of the economy to make cuts. It shows we need effective European and international measures to bring the aviation industry's emissions under control."
Green campaigners want aviation fuel to be taxed, and argue for higher levies on passenger tickets, with the money being spent on mitigating en vironmental damage. Airlines prefer the introduction of an emissions trading scheme, allowing them to share out their "entitlements" to pollution.
BA's social and environmental report also revealed that its diversity policy took a knock last year. The number of ethnic minorities in its workforce fell by 1.1% to 31.9%, suggesting that staff from minority backgrounds suffered disproportionately when 13,000 jobs were lost under the airline's "future size and shape" restructuring.
