Growing numbers of pilots are being taken ill after breathing polluted cabin air, according to the British Airline Pilots' Association (Balpa). It is to hold a conference next month in London to assess the threat to travellers.

Paul Tyler, the Liberal Democrat MP for Cornwall North, who will chair the conference, said pilots had fallen ill after breathing fumes and been forced to switch to an alternative oxygen supply. Balpa began monitoring cabin air quality after reports of long-term or disabling illness.

"There have been enough incidents of acute effects on pilots and aircrews of contaminated cabin air for us to be taking all the precautions we possibly can for the sake of travellers and crew," Mr Tyler said.

A spokesman for Balpa said some pilots felt the risks were growing as ultra long-range aircraft. such as the Airbus A340-500, capable of 18-hour non-stop flights, begin to enter the fleets.

"We're asking pilots to log incidents of contaminated air and we will be pushing the Government to do some more research on this."

Airbus, asked to respond, said no one was available to comment.

Mr Tyler heads an all-party group of MPs that wants stricter controls on poisonous chemicals such as organophosphates and carbon monoxide, which are associated with jet-engine fumes.

"Cabin air contamination poses a clear risk of long-term chronic illness for air passengers," he said.

Speakers at the conference will include the Rev John Woodley, a former Australian senator and chairman of a senate inquiry into the air safety and cabin air quality of the BAe 146, an aircraft used in the Queen's Flight. Dr Moira Summers will discuss the cases of more than 30 flight crew who have become ill after exposure to fumes aboard the 146.