Rain blamed for latest chaos in Heathrow queues

Revealed: failed airport eye scanners have cost £2 for every passenger who used them

The recent heavy rain across the south of England was the main cause of the chaotic scenes at Heathrow airport, the Government claimed yesterday as extra staff were drafted in to prevent huge queues building up again.

Ministers were accused of causing the problem of lengthy delays at passport checks by cutting numbers of border staff – and the London Mayor Boris Johnson said the crisis was giving "a terrible impression of the UK" to foreign visitors.

New arrivals at Heathrow's Terminal 5 said they waited more than two hours to be allowed into the country amid warnings that the airport was near breaking point. Travellers have been confronted with empty border control desks, with the delays exacerbated by the failure of iris scanners brought in to speed up the processing of passports.

Analysis by the Bureau of Investigative Journalism reveals that the iris recognition immigration system, which scans the unique patterns of travellers' eyes to confirm their identities, has cost just over £9m – but has only been used 4.7 million times, at a cost of £2 per passenger scanned.

The problems have intensified fears that London airports could struggle to cope with the tens of thousands of extra visitors heading to the capital for this summer's Olympics.

The Government insisted yesterday that urgent action was under way to plug the gaps at Heathrow – and pointed to recent prolonged rainfall as the reason for the disruption at Britain's busiest airport. Damian Green, the Immigration minister, told MPs that no passenger had had to queue for more than 90 minutes over the weekend, but conceded: "These times are too long. This was caused mainly by the severe weather leading to flight diversions and changing flight schedules and the bunching of arrivals."

Immigration officers were flown from Manchester to Heathrow to staff desks yesterday in an attempt to prevent a repeat of the disruption.

Mr Johnson wrote to Theresa May, the Home Secretary, to register his "serious concern" that the airport was "gaining such a poor reputation" and asked for reassurance that steps were under way to ensure it could handle the influx during the Olympics.

Keith Vaz, chairman of the Commons Home Affairs Select Committee, challenged Mr Green in the Commons to either hire more staff or reinstate targeted checks on travellers based on the potential risk they posed. Mr Vaz added: "The third option, which is to do nothing, is simply not acceptable."

The iris recognition immigration system, which scans the unique patterns of travellers' irises to confirm their identities, was introduced six years ago in an attempt to cut down on delays at passport control.

Earlier this year the Government said the costly system was being scrapped after revealing that the software used was already out of date. Birmingham and Manchester airports have stopped using the scanners. They are operational in Heathrow and Gatwick, however enrollment on to the scheme has stopped. Around 385,000 people are registered, according to information released by UKBA.

Despite costing £4.9m to develop and a £4.2m to run, the technology and new automatic passport scanning gates often fail.