Border Agency official condemns staff shortages
30 April 2012 Last updated at 22:48 BST
Immigration officers from Manchester have been rushed to Heathrow as passengers arriving at Britain's premier airport report long delays.
London Mayor Boris Johnson has raised concerns about the Olympics - saying the queues give a "terrible impression of the UK".
And a border agency employee has told the BBC that staff shortages are affecting security checks. But ministers insist security is paramount.
The BBC's Home Affairs Correspondent, Tom Symonds reports.