Ulster Bank has reported an operating loss of £242 million (€310 million) for the three months to the end of September.

The lender, owned by RBS, was hit by impairment losses of some £329 million (€410 million) which it said were related to its home mortgage portfolio for the most part.

The bank recorded a profit of £87 million (€110 million) in the three month period before impairment charges.

The bank has made a loss of £797 million (€994.3 million) in the first three quarters of the year, up from £771 million at the same point in 2011.

"The market remains difficult and we continue to see an elevated level of mortgage arrears," Ulster Bank chief executive Jim Brown said.

"We continue to work with our customers who are in financial difficulty on an individual basis to offer them appropriate support initiatives. We also continue to actively encourage our customers to contact us if they have any concerns about their financial health or are experiencing financial difficulty."

Ulster Bank said the cost of dealing with an IT glitch, which effected hundreds of thousands of customers across the RBS group earlier this year, has risen to £82 million (€102.3 million).

"This provision covers all operational costs associated with the incident, as well as redress of £41million (€52 million) to 750,000 customers across the island of Ireland," the bank said.

Ulster Bank said customer deposits remained flat on a constant currency basis and that there had been “no significant outflows” following “the technology incident”.

Retail and SME balances increased marginally in the quarter and the bank’s loan to deposit ratio improved by 3 per cent to 141 per cent.