The Queen visited Heathrow's new Terminal 5 earlier this month
Plans to fingerprint passengers travelling from Heathrow's new Terminal 5 have been suspended, less than 24 hours before it is due to open.
Airport operator BAA claims the measure is needed to distinguish domestic passengers from international ones.
But the data protection watchdog said the plan may breach British law.
The BBC's Tom Symonds said talks were now under way between the Information Commissioner and BAA, which insists it wants to bring in checks in the future.
Under the plans, prints would be checked at the gate to try to ensure the person who checked in was the same person who boarded the aircraft.
The move would allow domestic and international passengers to mingle in the terminal's departure lounge.
The idea behind the fingerprinting is to make it impossible for a terrorist to arrive at Heathrow on a transit flight, then exchange boarding passes with a colleague in the departure lounge and join a domestic flight to enter the UK without being checked by immigration authorities.
But the Information Commissioner's Office has warned such checks may be in breach of the Data Protection Act and asked why photographs could not be taken instead, as is standard practice at other airports.
BAA said the data was encrypted straight away and destroyed within 24 hours, in line with the act.
The Queen officially opened Terminal 5, which was subject to the UK's longest planning inquiry lasting four years, earlier this month.