But advocates say it will make travelling easier, while maintaining security.

Some Cathay Pacific and Emirates flights will invite passengers to join the trial when they check in.

Passengers' details are linked to their passport, so they can be fast-tracked past queues through security and boarding controls.

'More secure'

BAA said the system provided passengers with a type of "electronic key" which would allow them to pass easily through each stage of the airport's processes.

Steve Challis, head of product development for BAA, said: "Rather than having to continually show pieces of paper to prove who you are, or to prove entry to the next stage of a journey, then your electronic key should make things much faster and much more secure at the same time."

Immigration Minister Liam Byrne, launching the measures at Heathrow's Terminal 3, said the new system was crucial for security.

"Biometric ID systems are fundamental to securing our borders in a more mobile age," Mr Byrne said.

"They are crucial to our plans for counting everyone in and out of the country."

Mr Byrne went on to argue that the system is "a good example of how ID cards will be useful when helping people move through security".

All European nationals flying out of Heathrow's Terminal 3 will also be able to join the programme in its second phase.

Similar technology

In order to take part, they must hold a passport valid for at least six months, be over the age of 18 and fulfil UK government background checks.

A total of 13 different identifying scans of their fingerprints, irises and face will permit them to carry a membership card and allow them to use the system whenever they fly.

BBC transport correspondent Tom Symonds says similar biometric technology has already been installed in Dubai and Hong Kong.

It is hoped that, if successful, the system will be adopted at airports around the world.

It would enable passengers to pass through immigration controls by simply swiping their fingertips.

Simon Davies, of privacy watchdog, Privacy International, said: "The Home Office still hasn't got the message from international research that biometrics are extremely unstable and unreliable.

"At this early stage of biometric understanding this programme can have only extremely limited value."