From next year all passengers travelling on domestic BA flights from Heathrow will have to give their fingerprint and have their face scanned as part of the security check prior to take off.

The new biometric techniques, which will be introduced at Terminal 5 when it opens in March, were being implemented as a result of "recent security threats," airports operator BAA said. Similar procedures are already in force in other countries, such as the US.

BAA said the checks, which will take place at the normal security point and then again immediately prior to boarding, had become necessary because Terminal 5 had a common departure lounge for international and domestic passengers.

Such lounges left open the possibility that a passenger arriving on an international flight could board a domestic flight from the common area and evade immigration control.

"Up until now there's always been separate departure lounges at Heathrow," a BAA spokesman said. "The problem is that an international passenger arriving at Heathrow who is supposed to be transferring to Helsinki, say, could possibly board a flight to Edinburgh and thus avoid immigration."

Existing terminals which have common lounges for international and domestic passengers, such as Gatwick, get around this problem by requiring all domestic passengers to have a photo taken, which is then printed on their boarding pass.

The spokesman added that while there were no plans yet to introduce biometric security checks across all airports such checks were "definitely the way of the future".

The new machinery at Terminal 5 also had the potential to synchronise with other databases, so that a passenger's biometric information could instantly be checked against, for instance, an ID card database.

Biometric screening is just one of a range of security measures that will be introduced at Terminal 5, a tour of the as-yet-unfinished facility taken by Times Online revealed.

As many as 120 archway detectors deploying the latest X-ray technology will screen the 70,000-80,000 passengers who will pass through the terminal each day. The CCTV network will also be "one of the largest in the UK", BAA said.

All taxis picking up and dropping off passengers will be required to have a radio frequency identification tag fitted so that their movements can be tracked while embedded sensors underneath all the roads will provide additional monitoring.

Starting in September, more than 14,000 people will take part in trials of the facility. The site, which is the size of Hyde Park, is due to open on March 27.

BAA said that the £4.3 billion project, which began construction in 2002, was currently on budget.