Allied Irish Banks (AIB) has today announced that it is to close 67 branches across the country.
The bank confirmed that 51 locations will cease operations by the end of the year, with the remaining 16 closing in 2013.
An AIB spokeswoman insisted there will be no compulsory redundancies.
"Staff are going to be redeployed as part of the restructuring," said the spokeswoman.
"We have around 346 people working in the affected branches. Not all of them are full-time members of staff."
AIB also announced it is raising its standard variable mortgage interest rate by 0.5%.
A further five branches at AIB's subsidiary First Trust Bank in the North have also been earmarked for closure.
"AIB is changing in response to customer needs," said Denis O’Callaghan, head of AIB branch banking.
"We have seen a very significant change in the way our customers wish to do their banking. As a result of this, many of our branches have seen a large decline in customer visits.
"Notwithstanding today’s announcement, branches will remain an important part of AIB’s overall distribution strategy and will be complemented by an enhanced online service."
Finance union the Irish Bank Officials Association (IBOA) described today's announcement as "traumatic" for the workforce.
General secretary Larry Broderick said the closures reflect a piecemeal dismantling of Ireland's banking infrastructure.
"It will also come as a major shock to customers in these areas - who have come to rely on the service from their local branch," said Mr Broderick.
He said AIB has shown no regard for communities and the customers it serves, and there was a danger of some Irish towns ending up with no more than an ATM.
Among the 67 affected branches are six amalgamations and the closure of 45 sub offices, which the bank describes as smaller branches.
Those will close this year, with the first shutting its doors on October 12, the bank confirmed.
The remaining 16 outlets will close in 2013.
AIB chief executive David Duffy said the closures were necessary to allow AIB to continue providing credit to the economy at sustainable levels, after the bank today announced an operating loss of €1.1bn in the six months to the end of June.
He insisted there would be little inconvenience to customers due to a recent deal struck with An Post, which has agreed to extend banking facilities.
Customers will be able to lodge cheques and deposits at post offices across the country, which the bank claims could minimise disruption.
Mr Duffy added that staff at the branches will continue to play "a critical role" as AIB works to regain the public's trust.
The bank announced plans in March to lay off 2,500 staff members - one in six of its workforce - by the end of 2013.
Its aim is to save €170m a year. Half the redundancies will be made this year and the other half next.
But the bank insisted no-one will lose their job as a direct result of these closures.
Earlier this week, State-controlled Permanent TSB confirmed it is to cut 250 jobs and close 16 branches in the near future.
The bank, which currently operates 92 branches across the country, hopes to reduce operating costs by 10%.