Former Christian Aid worker Mike Lacey said he and two other demonstrators were stopped and detained by police for wearing T-shirts that opposed airport officials' plans to add a third runway at Heathrow, the Mail on Sunday reported.

"The process took half an hour and the police were unable to give any justification for their behavior," Lacey said of the May 31 incident.

The trio, which also included John and Tessa Wilding, were stopped on their way to the protest to join 3,000 other demonstrators.

A spokeswoman for Scotland Yard said the trio were stopped and eventually removed from airport property based on a 1996 bylaw that allows police to question anyone at the airport they find suspicious.

"Three people were stopped and asked to account for their presence," the unidentified spokeswoman told the Mail. "They were not searched. The officers correctly interpreted the bylaws."