Detectives in the Republic have told Louis Walsh that his phone was hacked by a phone employee who read his messages.

The impresario and X Factor judge was one of at least two people whose mobile was monitored by the man. His activities were discovered by the phone company who in turn tipped off gardai.

A shocked Louis said: “I don't know how much personal information he managed to gather or how long it was going on.”

Confidential information in Louis' and in Irish TV presenter Glenda Gilson's personal phones may have been obtained in the incident, it is understood.

Detectives launched a probe after receiving a report that an individual had made an attempt to access Walsh's phone records.

They are unsure whether it was the actions of a stalker or whether the information was being used for commercial gain.

Gardai are also investigating an attempt to access the records of Ms Gilson — with fears that the same person could have attempted to hack into both phones.

The motive for the alleged hacking is not clear at present.

A shaken Louis said that he was informed that his mobile was tapped into by a staff member of Vodafone, his service provider.

The celebrities' text messages and voice mail messages may have been broken into. Walsh is considering taking legal action.

“I knew nothing about it at all until the boss of the company contacted me. I was told an employee had hacked my phone,” Louis said.

“The same person had hacked into Glenda Gilson's phone and maybe others. The last I heard, the matter was with gardai and there would be a court case. I don't know how much personal information he managed to gather or how long it was going on.”

The music mogul said that he couldn't be sure of the extent of what the individual was able to monitor on his phone.

He added: “It makes me very wary of exchanging confidential information by phone and yet it's hard to avoid it, given the nature of this business,” he added.

When contacted, Gilson said that she didn't wish to comment on the matter.

Gardai launched a full investigation, which is ongoing. Phone tampering is an offence under the Data Protection Act.