Irish financial institutions have insisted that they were only notified about a security threat to 3,000 credit cards last week, despite the fact that Visa International became aware of the breach two months earlier.

The two biggest credit card issuers, AIB and Bank of Ireland, said they were formally notified that cards held by a large number of their customers may have been compromised early last week and immediately began to notify cardholders.

Customers who were likely to have been affected were those who had used their credit cards in the US 12-18 months ago. The Irish financial institution began to cancel the affected cards and have been issuing new ones.

A Visa International spokeswoman said the latest date that it became aware of the problem was April 30th last and that it would have immediately alerted financial institutions that are part of its network. She added that it was up to banks and building societies to deal with the information as they wished.

This statement has annoyed the Irish financial institutions, which insist that Visa did not pass on the alert until last week. "We were alerted probably on the Monday or Tuesday," an AIB spokesman said.

Mr Eddie Ryan of Bank of Ireland's credit card division said its security division had also received that information last week. "We will be taking it up with our representatives to try to find out the cause for this delay."

So far very few Irish credit cardholders have been affected by fraudulent activity perpetrated by criminals who have stolen their details, the banks say.