The British Airline Pilots' Association (Balpa) said that the proposal, backed by the European parliament, could add up to two hours to a pilot's working day. Balpa's chairman, Mervyn Gramshaw, said this would leave his members unable to behave in an "intellectually sensible" way. Their concentration levels would be equivalent to a blood-alcohol level above drink-drive limits.

Mr Gramshaw, a Britannia Airways pilot, said: "Lives are at risk and will be put at risk."

Under present regulations, a British pilot starting during the day, with two flights scheduled, is allowed to spend 13 hours at the controls. The Brussels plan would impose a Europe-wide "cap" of 14 hours or more.

For pilots beginning at night, the European limit would be more than 12 hours, compared with Britain's limit of 10 hours.

Mr Gramshaw compared the safety risk to the long hours worked by over-tired junior doctors: "They kill the patients one at a time. We tend to kill ours hundreds at a time."

The harmonisation plan, put forward by Labour MEP Brian Simpson, has been passed by the European parliament. The council of ministers will decide in the spring whether to turn it into law.

Mr Simpson said yesterday that he took "everything Balpa says with a pinch of salt", and claimed his plan provided a "framework within which all countries have to operate", but insisted Britain could keep its stricter regulations.

Opponents fear the framework will lead to fierce lobbying from airlines to liberalise Britain's restrictions in line with other European countries, some of which have virtually no legal limit on pilots' hours.