The surveillance equipment had been left in the judges' room, where Simon Cowell, Amanda Holden and Piers Morgan embarked on a second day of filming.

Suspicions were aroused when the device caused interference with the sound and film equipment for the recording of the audition process of the hit Saturday night ITV1 show.

When the equipment was found police were called to the venue, the Palace Theatre in Manchester, where fire-eaters, acrobats, dancers and singers are hoping to get the chance to make their name on the show.

There was a 20-minute delay in filming as police investigated.

Cowell said afterwards: "This shows the extent to which people will go to to get inside knowledge on what is going on."

TV bosses believe there is a possibility that a freelance journalist could have planted the device to find out what was being said in the judges' room.

A statement from Greater Manchester Police said: "While officers were at the theatre investigating this incident, they were asked by theatre management to advise a 45-year-old man that he would be ejected because he had unauthorised access.

"The man's details were checked and he was arrested in connection with an unconnected speeding offence."

Last year, former Carphone Warehouse manager Paul Potts won a record deal and the chance to perform at Royal Variety Performance in front of the Queen.