London is bracing itself for the start of the Olympic rush on Monday with the first wave of tourists, officials and athletes expected to arrive at Heathrow amid growing anxiety about airport's ability to cope with the influx of visitors.
Officials said around 40,000 extra passengers are due to touch down in the UK as dedicated Olympic lanes are opened to transport VIPs into central London.
An extra 500 border control staff have been drafted in to help ease congestion in immigration halls at Heathrow, but last week John Vine, the chief inspector of borders and immigration, warned that temporary staff processed passengers more slowly while asking fewer questions.
Fears that new staff were not up to the job were exacerbated on following reports in the Observer that terror suspects are entering the UK ahead of the Olympics because inexperienced staff had failed to carry out the proper security checks.
Speaking on condition of anonymity, the UK Border Agency official claimed three terror suspects had been waved through by staff on his shifts since the start of July.
All were registered on the Home Office suspect index system. Another employee alleged that staff had missed five suspects in just one day earlier this month.
The senior official told the newspaper: "The missing of counter-terrorism 'hits' is a huge thing, but new recruits are not getting enough time to be taught."
A Border Force spokesman said all staff were "fully aware of the checks they needed to conduct and that all checks were being completed".
He added: "All contingency staff deployed to the border are fully trained and supported by experienced Border Force officers at all times. Border Force has already delivered real improvements at Heathrow and is transforming the way it works to deliver improved waiting times and a secure border."
Fears over Heathrow's ability to cope with the influx of 2012 visitors comes as the first dedicated Olympic lane opens on a stretch of the M4 on Monday. There have been fears that the work on the damaged flyover near junction 2 of the motorway in west London would not be completed in time. But the affected stretch was reopened three days ago and the Games lane will be operational for 3.5 miles between junctions 3 and 2 on the London-bound carriageway between 5am and 10pm from Monday.
The M4 lane is part of a wider Olympic route network (ORN) that will provide exclusive access for members of the "Games family" including athletes, their officials and equipment between Heathrow and the Olympic village in Stratford, east London. Officials say they expect around 80% of athletes and officials to use these lanes, which have been criticised by campaigners who say they are elitist and will stop ordinary Londoners moving freely around the capital.
The ORN network will be fully operational by 25 July – two days before the Olympic opening ceremony. Officials say they will be clearly marked and will operate alongside existing traffic and warned that unaccredited drivers who stray into the lanes face a penalty charge of £130.
