This comes after similar delays in April, where disgruntled passengers passed officials without having their documents checked in protest.
To ease the pressure, the Border Agency is to open separate lanes for non-European passengers entering the UK who are considered "low risk" and do not require visas, the Telegraph reported. This will include many New Zealand passengers, as well as fliers from Australia, the United States, Japan and Canada.
A report by independent chief inspector of borders and immigration, John Vine, found the delays were exacerbated by job cuts, as well as staff going home at the airport's busiest times.
The airport is expecting its busiest day in history on August 13, the day after the Olympic closing ceremony, with 138,000 passengers expected. The airport normally averages 95,000 departing passengers a day.
However some countries' Olympic teams, including Australia, China and Canada, are booking private charter flights from Stansted in Essex to avoid the congestion.
New Zealand's Olympic squad will fly out of Heathrow.