Facial recognition scanners are being trialled at an airport as part of government efforts to improve security and reduce passenger congestion.
The system has been introduced at Manchester Airport. It can be used by adult biometric passport holders from the UK and European Economic Area.
It works by scanning passengers’ faces and comparing it to the photograph digitally stored on their passports.
The Lib Dems said the government must ensure the technology is “foolproof”.
Facial recognition technology is part of the Home Office’s e-Borders programme, which is aimed at transforming the UK’s border control to ensure greater security and efficiency.
Ministers believe the facial recognition technology will help identify criminals and terrorists trying to enter the UK illegally.
About 13 million people in the UK have been issued with a biometric passport, which contains a microchip holding biographical information and images.
And a further 30 million people living in the European Economic Area, which incorporates the EU countries plus Iceland, Liechtenstein, Norway and Switzerland, have biometric passports.
At Manchester Airport, passengers with biometric passports will avoid queues and pass through unmanned gates.
A scanner checks their passport has not been tampered with and that they are not on any security lists.
They are then allowed through to the next gate, where a facial recognition scanner reads their face.
Rejected passengers are redirected to immigration officers for further checks.
Liberal Democrat home affairs spokesman Tom Brake voiced concerns over the reliability of the technology.
“Ministers must ensure that this technology is foolproof. If this goes wrong, thousands of passengers could be left stranded at Manchester Airport,” he said.
“Following the Heathrow Terminal 5 embarrassment, the last thing this country needs is another major transport hub grinding to a halt.”
The system will be introduced at Stansted in September, and if the trials are successful it will be extended to all major UK airports.
All new UK passports have been biometric for the past two years and the Home Office estimates about seven million people will receive one every year.