The Ulster Bank’s treatment of its customers is to be probed by the powerful Treasury Select Committee in the House of Commons, it has been revealed.

MPs on the committee are to look into a complaint the bank is not fulfiling the commitments made by its parent bank to its Northern Ireland customers.

The bank is a wholly owned subsidiary of the Royal Bank of Scotland (RBS) and according to SDLP leader Mark Durkan, it is dragging its heels in implementing pledges made by RBS.

However, the Ulster Bank said it was doing just what was promised by RBS — and had told Mr Durkan so before Christmas.

Mr Durkan said he had written to committee chairman John McFall before the Christmas recess expressing his concerns that Ulster Bank customers were not benefiting from a series of promises made at the end of November and start of December by the RBS Group.

He welcomed a reply from Mr McFall confirming the committee would be “looking into the role and behaviour of the Ulster Bank”.

On November 23 last year RBS Group announced that it was not going to increase pricing on committed overdrafts until at least the end of 2009 and to guarantee availability of committed overdrafts for one year for business banking customers with turnover of under £1m, he said.

Mr Durkan added: “In addition the RBS Group made a further statement on December 1, 2008, in which it guaranteed not to initiate repossessions of homes for six months after mortgage customers fell into arrears. It also pledged to maintain this position until the end of 2009.

“However the same commitments have not yet been made by its Northern Ireland subsidiary.”

In a statement the bank said: “Ulster Bank has adopted the terms of RBS's recent pledge on the certainty of overdraft limits for some time, and is committed to maintaining existing overdraft limits for its SME customers unless there are exceptional circumstances.

“We are also committed to maintaining margins for our SME customers whose risk profile is unchanged.

“Regarding action for mortgage repossession, Ulster Bank made the same commitment as our parent company RBS at the same time, December 1th, 2008.

“Ulster Bank Group contacted Mr Durkan's office on December 19th to clarify these matters with him.”