More than 237,000 families across Northern Ireland were put on alert today after it was confirmed that their personal details - including bank account details - were included on two lost Government computer discs.
HM Revenue and Customs confirmed to the Belfast Telegraph that the details of every family in the province in receipt of child benefits at the time the discs went missing last month would have been among the missing information.
At the last official count in August, there were 237,700 families in Northern Ireland claiming benefits for 446,000 children under the age of 16.
The missing records include parents' and children's names, addresses, dates of birth, child benefit and national insurance numbers and, in some cases, bank and building society details. Fears have been raised that they could have fallen into the hands of criminals.
A spokeswoman for HMRC in Belfast said it was "safe to assume that the vast majority of those 237,000 customers" were caught up in the debacle which has seen the details of 25m individuals UK-wide lost.
She said that families who had begun claiming child benefit after the discs went missing on October 18 were not affected.
"We will be making contact with all customers in Northern Ireland about this," she added.
DUP MP Peter Robinson has urged child benefit claimants to "be very vigilant and to monitor their bank statements".
"This is an extremely serious incident where the identity and personal details of millions have been compromised," said Mr Robinson.
"It is possible that these details could have fallen into the hands of criminals. Identity fraud is already an enormous criminal trade and child benefit recipients in the province should not underestimate the seriousness of this situation.
"It is important that HMRC contact all individuals affected by this breach as soon as possible."
"Undoubtedly this news will cause significant worry to people across the country and HMRC has a duty to offer assistance and advice to these individuals, " added the MP.
The DUP minister was speaking from Westminster after Chancellor Alistair Darling sent shockwaves through the House of Commons with an admission that two discs containing the records of 25 million families had been lost while being transported by a courier.
In an emergency statement, he apologised for what he described as an " extremely serious failure on the part of HMRC to protect sensitive personal data entrusted to it in breach of its own guidelines".
A spokesman for the HMRC in London confirmed that parents in Northern Ireland were caught in the debacle.
The chairman of HM Revenue and Customs, Paul Gray, resigned yesterday.