Amicus said allegations made against the men were "completely without foundation".

The men were dismissed over claims of unauthorised absence, falsification of records and security breaches.

An airport spokesman said the decision to dismiss them for gross misconduct had been upheld following an appeal.

He said: "Airport workers are placed in a position of trust and responsibility, and are aware of the implications, should such trust be abused.

'All out strike'

"The airport places the safety and security of its staff and passengers above all other considerations."

But Amicus, which represents more than 200 workers at the airport, said management claims were "unsubstantiated" and has demanded the reinstatement of the men, who have 52 years of service between them.

The union claimed covert surveillance techniques used by airport authorities to substantiate its case were a breach of Data Protection and Human Rights legislation.

Peter Coulson, of Amicus, said: "The union totally refutes the allegations made against these men.

"The workers in question enjoy wide support among their colleagues and we will be looking to conduct an industrial action ballot in the next week with a view to an all out strike before Christmas."

Mr Coulson said although their appeal process had been exhausted, Amicus would be pursuing claims on behalf of the men for unfair dismissal.