DETECTIVES have told Louis Walsh that his phone was hacked by a phone employee who was reading all his messages.
The pop manager 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 today: ""I don't know how much personal information he managed to gather or how long it was going on."
He confirmed to the Herald that a garda investigation is now under way.
Confidential information in Louis' and in Xpose 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 the X Factor judge'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 model Glenda 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 and now Louis said that he 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.
"What measures are in place to stop this happening?," Louis said. "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 into the incident, which is ongoing today. Phone tampering is an offence under the Data Protection Act.
This is the first time that a mobile phone hacking scandal has hit Irish celebrities -- but it has been going on in Britain for the past number of years.
The former royal editor with the News of the World, Clive Goodman, along with private investigator Glen Mulcaire were jailed in 2007 after the phone messages of aides to Britain's Prince William were illegally intercepted. The controversy involved eight celebrities.
Other victims of phone hacking have included supermodel Elle McPherson and Gwyneth Paltrow alongside George Michael, ex-England manager Sven-Goran Eriksson and Britain's former deputy prime minister, John Prescott.
Speaking about what happened to him last year, PR guru Max Clifford described it as a devastating experience.
"The police did make me aware my phone was being tapped but it was my mobile phone provider that initially told me about potential irregularities but how long it had been going on for, I don't know," he said.
Members of the public can lodge complaints with the Data Protection Commissioner, if they feel there has been a breach of their personal data.
A data controller found guilty of an offence can be fined amounts up to a €100,000 if convicted and may be ordered to delete part of a database if relevant to the offence.