Heathrow Terminal 5 client BAA has stepped up drug testing on the flagship site after random checks suggested that many workers could be working under the influence of drugs and alcohol.
It emerged this week that a series of random tests showed about 6% of those tested were positive for alcohol and drugs including cannabis and cocaine. The figure raises concerns that many more of the project's 8600 workers could be working under the influence of drugs and alcohol.
BAA has now introduced monthly random tests in a bid to curb drug and alcohol use on the site.
A spokesperson confirmed: "To ensure that Terminal 5 remains drug and alcohol free, the number of random tests undertaken was recently increased.
The evidence of drugs and alcohol use has however fallen since the project began.