Chief executive Cormac McCarthy said Ulster has already imported RBS products from Britain and America for corporate and business customers. He said new retail products, including savings accounts and mortgages, would follow over the next two years.

McCarthy said Ulster will tap RBS's know-how to beef up its presence in wealth management and bancassurance, which involves selling pensions and investments to its banking customers.

"We're very clear about wanting to be number one in this market, " he said.

"Because we have the backing of a parent such as RBS, nobody else can take on the big two Irish banks like we can."

The new offset mortgage, which aims to save borrowers money by balancing their cash against their debts when calculating interest, is due to be launched before the end of the year. The idea is similar to the current account mortgage pioneered by First Active shortly before it was acquired by RBS for 887m in 2004.

That product caused controversy recently after some borrowers objected to First Active's decision to change the terms and conditions. It is understood the unpopular move was in preparation for the switch to the new RBSstyle offset mortgage.

On Friday, Ulster Bank reported a 20% jump in operating profits to £182m ( 263m) for the first six months of the year. Mortgage lending soared by 30%, with Ulster Bank and First Active being the first lenders to offer 100% mortgages, which allow first-time buyers to borrow the full cost of buying their homes.

McCarthy said the controversial loans, which have drawn frequent criticism from housing minister Noel Ahern, were not a big contributor to the mortgage growth.

"There's been more heat generated by 100% mortgages than light, " he said. "We don't disclose the make-up of our mortgage book but you'd be surprised by how little is for more than 90% of the value of the houses being purchased.

We're a prudent lender and this is not a huge part of our business."

AIB raised serious questions about the risks in 100% mortgages when reporting its interim results last Tuesday, claiming it would rather lose business than lend to people who cannot afford a substantial deposit.

"We act in a very restrained fashion with 100% mortgages and they only account for about 1% of our mortgage book, " said finance director John O'Donnell. "That's about one-third of the exposure of one of our main competitors.

We're paid a price for this restraint because our mortgage business is growing by about 3% less than the market as a whole."