Items are said to have been smuggled past security

Plain clothed officers from the Department of Transport are understood to have managed to pass devices through the airport's x-ray machines and take them into the cabin of an airplane.

A spokesman for the transport department said it was within its rights to carry out such tests at any time, but would not confirm if this specific incident took place.

BAA, which owns Edinburgh airport, would not comment on the details either, but said security is given the highest priority at all times.

A Scottish newspaper described the objects as "bomb-like" and reports that the devices had been hidden inside a laptop computer and a hairdryer before being put into luggage for the test last month.

Edinburgh, which handles almost seven million passengers a year, is part of the British Airports Authority, which also runs Glasgow, Aberdeen, Heathrow, Gatwick, Stansted and Southampton.

Since September 11, 2001, BAA has confiscated nearly 13 million items which are not permitted on board aircraft BAA

Edinburgh Airport bosses promised to tighten security four years ago after explosives, guns and knives were carried undetected through checkpoints in a similar operation by Transport Department staff.

A spokesman for BAA in Scotland said security at all UK terminals was tested "regularly and rigorously", using constantly updated methods, with the support of the industry.

"Test results are only one of many control measures used to improve and enhance security systems across the airport," he added.

"Airport security is more than metal detectors and personal searches. There are many layers, including 100% hold baggage screening, and close cooperation with the police and control authorities to identify specific threats.

"We never comment on specific details of security processes other than to say that this area is given the highest priority at all times.