Permanent TSB has confirmed it will axe 280 jobs over the coming months.
The country's largest mortgage provider also plans to redeploy another 100 staff from its branches and head office to its online and telephone operations.
The bank, which employs 1,850 people, has already cut 400 jobs in the past two years.
It maintained that no branches will close as a direct result of its restructuring programme, but more customers would use its automated services.
Elsewhere, the bank confirmed that homeowners with a standard variable mortgage will be hit with a 1% rise, hiking its average repayments by an extra 33 euro a month.
David Guinane, chief executive of Permanent TSB bank, said the two moves were a major part of the bank's plans to return to profitability by reconfiguring its operations in light of higher costs and reduced business volumes.
"We're entering a new period for banking in Ireland and we have to ensure that Permanent TSB bank is correctly sized and has the correct margins for the market conditions we are operating in at present," he said.
The Unite trade union, which represents 1,200 of its workers, said it is shocked and angered at the scale of the job losses, saying the axed workers are "being forced to pay for the reckless mismanagement of the bank in recent years".
Regional co-ordinator Walter Cullen, who held crisis talks with management on Thursday, added that he believes the bank is seeking 360 voluntary redundancies and that talk of redeployment was a smokescreen for cuts.
He went on: "This is a dark day for staff who will also be dealing, as they have in the past, with the pain and anger of customers affected by the mortgage rate increases."