CaixaBank is planning over 8000 job cuts and the closure of 1530 branches following its merger with Bankia.
The cuts, branded as "savage" by union representatives, will reduce employee numbers by 18.7% to 36,109, down from 44,000. The branch closures will hit a quarter of the combined banking network.
Caixabank says that the workforce cull is based on "production and organisational grounds, given the overlaps and synergies derived from the merger and the current market circumstances".
The bank is currently negotiating with union bosses over its proposals, which includes a voluntary redundancy limit of 50% on workers over the age of 50 so as not to lose experienced staff.