Allied Irish Bank, parent company of Northern Ireland bank First Trust, is expected to announce 2,500 job losses as early as this week.
The figure is 25% higher than signalled in April 2011 and it is understood that some of the losses will hit building society EBS, which merged with the bank in July.
According to Bloomberg news, the losses are imminent.
Unions fear up to 400 jobs in Northern Ireland could be at risk at some of the 48 First Trust branches here.
AIB (UK), of which First Trust is part of, employs just over 2,000 staff.
A spokeswoman for AIB and a spokesman for the Republic's Department of Finance both refused to comment on the job losses.
AIB has been selling off assets and the Irish state owns over 9% of the bank.
First Trust staff in Northern Ireland were initially being told to expect news on the job cuts later this month.
Last April, AIB warned it was planning to shed 2,000 staff at both banks.
And on Monday, AIB said it was still in discussions with the Department of Finance in Dublin over the extent of the impending restructuring package that will lead to job losses.
Earlier this week, it was revealed that AIB chief executive David Duffy had e-mailed staff with plans to streamline AIB's functions.
News of the consolidation suggests AIB is close to making an announcement on its long-awaited redundancies, since the new centralised functions are likely to need fewer staff.