The head of the Ulster Bank has warned of future branch closures in response to a huge ongoing shift towards online banking.

Chief executive Jim Brown, who was giving evidence to a Westminster committee investigating banking practices in Northern Ireland yesterday, said in the last three months of 2013 only 16% of transactions took place in a branch setting.

The bank's parent company RBS is currently carrying out a review of the business - the outcome of which is expected within weeks.

Last year the bank closed 22 branches and sub-offices on the island of Ireland and had said more closures could follow.

"The key thing here is that customer behaviour is changing rapidly," Mr Brown told the Northern Ireland Affairs Committee yesterday.

He said more and more people were using on-line banking, particularly through their phones.

"There has been a huge shift over a very short period of time to that area, and it's not just in terms of transactions, it's customers opening accounts and so on," he said.

"There has been some changes to the branch network as the result of that - some closures - and I expect, over time, there will be more, but it is really driven by customer demand," Mr Brown added.

A banking union recently warned its members that the RBS review could lead to job losses. The Irish Bank Officials' Association has expressed fears the exercise would trigger redundancies.

While Mr Brown said Ulster Bank did not have any specific plans over redundancies "at this stage" he stressed that view was subject to the outcome of the RBS review.

During his appearance at Westminster, Mr Brown also denied allegations made by a government adviser that Ulster Bank had been involved in bankrupting viable businesses to make profit.

The claims made by businessman Lawrence Tomlinson, in a report to Business Secretary Vince Cable, focused primarily on the actions of a division of RBS and Ulster Bank that dealt with high risk loans.

Mr Tomlinson said there was evidence businesses were pushed into the Global Restructuring Group (GRG) to make more profit for the banks through fees and ultimately, after default, through obtaining customers' devalued assets.

In the wake of the report, Ulster Bank claimed Mr Tomlinson's report was in regard to RBS operations.

But Mr Tomlinson later made clear that specific allegations against Ulster Bank were included in his report and "dossier of evidence".

Mr Brown told committee members said he had seen no evidence to support the claims. "We take these allegations very seriously of course," he said, noting that RBS had commissioned a legal firm to investigate the claims.

"From my own perspective I have seen no evidence of any systematic issues of the nature Mr Tomlinson has talked about and no cases have actually been presented to us to actually review to see if there has been any issues," he added.

As well as the RBS commissioned investigation, regulators are carrying out an independent probe of Mr Tomlinson's allegations.

Mr Brown claimed the government adviser did not "engage" with the bank before he published his report.

"None of the allegations have been presented to Ulster Bank to review to confirm or deny," he added.

Mr Brown was accompanied by the head of the Ulster Bank in Northern Ireland Ellvena Graham.

They were quizzed by committee members on the various IT failures that have hit Ulster Bank in recent years, including a major meltdown in 2012 that left customers with limited access to their accounts for three weeks.

Ms Graham assured the committee lessons had been learned, but said it would take some more time for all the technology improvements to be implemented.

"I am very acutely aware of the damage to the brand through the IT issues," she said. "We took a hard time in 2012 and I am very aware - my primary objective is to try and improve that and make it a place that staff are proud to work in."