Lloyds Banking Group will make about 15,000 job cuts, including back office jobs, as part of an overhaul of its business following a major review.
The back office and middle office are likely to see major cuts, as the bank said it will retain the current level of branches.
In the summer of 2009, union Unite accused Lloyds of having a strategy of death by a thousand cuts.
David Fleming, Unite national officer, said: "Astonishingly, one in eight roles will be lost over the next three years. This review is merely another box-ticking exercise to give this bank an excuse to sack more employees."
Since Lloyds TSB took over HBOS in a government-brokered deal in 2008, it has cut about 27,000 jobs.
"Today, Lloyds Banking Group is simply attacking the workforce who service local communities and deliver the highest levels of service to the consumers of the bank," added Fleming. "This review does nothing to deal with the structural challenges facing the organisation."
In the review, the bank also said that better end-to-end processes and IT platforms will contribute £1.5bn of annual savings. This will involve rationalising multiple systems acquired when Lloyds Banking Group took over other finance firms.
But Steve Tatlow, assistant general secretary at the Lloyds TSB Group union, said operational roles at Lloyds Banking Group do not include IT jobs and there is likely to be more offshoring of IT, particularly as the bank attempts to reduce the number of different banking platforms it uses.
He called for the bank to complete the IT work in the UK: "The work should be carried out in the UK rather than sending it to India to do it on the cheap."
Last year, the bank also told its IT contractors to accept a 15% drop in pay.