Hit squads of temporary Border Force staff are unaware which countries are in the European Union and are failing to spot forged passports, whistle-blowers have claimed.
Up to 500 extra people are being deployed to prevent a repetition of the huge immigration queues at Heathrow.
As reinforcements arrive in the run-up to the Olympics, The Daily Telegraph can disclose alarming errors have been made.
Within five minutes of starting work on a desk, one member of the contingency team struggled when being asked to process passengers from a flight from Budapest, asking whether Ukraine was part of the EU.
There are also fears that temporary staff do not understand the Warnings Index, a Home Office database which shows people with suspect immigration histories or who should be subjected to closer scrutiny.
it was reported yesterday that this may have led to a number of terrorist suspects gaining entry into Britain.