The news was revealed today after Irish Life and Permanent Ltd reported a loss of €424 million for 2011 after setting aside €1.4 billion in loan losses.
The residential mortgage arrears figure of 12% is well above the industry standard, with AIB reporting arrears of just 8% last week.
Commenting on the results, the bank blamed “significant deterioration” in its mortgage book and a greater peak to trough assumption for the decline.
Chairman Alan Cook said the banking group’s performance reflected the “difficult economic environment” and rising impairment charges in its Irish mortgage book.
“The bank has successfully managed its funding requirements through the year and has made considerable progress in preparing the business for the future in a changed banking market,” he said.
“A key challenge for the business and for our customers is arrears and we are working hard to manage this situation with our customers and with other stakeholders.”