VODAFONE IRELAND, the State's largest mobile phone operator, has apologised to its customers after a fault on its system led to some 1,000 subscribers accessing voicemails left on other subscribers' phones.

The company, which has more than 2.26 million subscribers, said the voicemail service for some 220,000 of its customers was shut down for four hours on Monday of last week while repairs were undertaken. The fault related to a specific group of phone numbers issued by Vodafone to subscribers with prepaid contracts and top-up phones, said a spokeswoman for the company.

Vodafone was alerted to the problem when customers contacted its help desk, she added.

She said that a "random" fault had occurred for a period between Sunday, March 2nd, and Monday, March 3rd. "It was rectified by 5pm on Monday."

She said the Office of the Data Protection Commissioner was informed about the incident on the day it occurred, and was advised when full service was restored.

The Irish Times was unable last night to make contact with the Office of the Data Protection Commissioner.

Vodafone Ireland said in a statement that "a very small proportion" of its customers encountered a technical problem with voicemail services last week.

"When the issue was discovered, Vodafone took immediate steps to rectify the situation, and full service was restored within four hours," the statement said.

"The company wishes to apologise to any customers impacted, and would like to point out that this was a highly-irregular incident that only occurred for a very short period of time and impacted a very limited number of customers."