Abbey, the UK bank now owned by Spain's Banco Santander, is threatening to axe 335 IT staff from its operations in Glasgow, Milton Keynes and Belfast.
The cuts are part of a restructuring implemented by new Spanish owner Banco Santander Central Hispano, which includes 3000 jobs losses across the enterprise.
Abbey says the move affects around 200 IT staff at its Milton Keynes centre, 85 in Belfast and 50 in Glasgow. All affected staff have been told that they are at "risk of redundancy".
Under the plans a further 150 IT employees will be offered roles within Isban, a division set up in Milton Keynes by Santander to roll out its own Partenon banking platform across Abbey's operations. In addition, 90 technology staff currently working at Abbey's online banking division Cahoot and business banking department will also transfer to Isban.
Financial services union Amicus condemned the job cuts, which come just months after Santander's takeover. The union told reporters it was sceptical about the offer of a transfer to Santander's Isban subsidiary, saying that just five per cent of staff accepted an earlier transfer offer to move from Abbey's Edinburgh operations to Glasgow.