The bank, which has already shed 40,000 roles since a £45 billion taxpayer bail-out at the height of the financial crisis in 2008, is expected to bring in a further round of cuts next month as it aims to cut costs by £1bn. The part-taxpayer owned bank confirmed that it is to cut its current 65% cost-to-income ratio with a target in the mid-50s, two months after its latest results showed it made a third quarter pre-tax loss of £720m.
That would mean slashing the bank's £10.06bn operating costs -more than half of which is made up of staff salaries.
The news has shocked Unite who have called for discussions over the latest cost-cutting proposals.
"We have asked for talks with RBS today before they make any announcement or decisions over job losses," said a Unite source.
Unite national officer for finance Dominic Hook described the reports as "worrying".
He added: "Our members have borne the brunt of the management's mistakes that necessitated the taxpayer bailout in 2008 - and we feel that: 'Enough is enough'. About 40,000 workers have already lost their jobs and RBS should draw a line in the sand on job cuts.
"Many of our members earn as little as £16,000 a year and this has gone hand in hand with increased workloads, unpaid overtime and great pressure to perform and sell financial products.
"We call on the RBS management to engage with Unite in a constructive fashion over its future plans and acknowledge that an organisation's greatest asset is its people, rather than employees hearing of the group's plans via leaks to the press."
The new cost-cutting Project Cook measures are expected to be finalised when RBS's annual results are revealed in six weeks time
The code name is believed to be a reference to Captain James Cook, the British explorer and navigator explorer who achieved the first recorded European contact with the eastern coastline of Australia in April, 1770.
It is believed to be a nod to chief executive Ross McEwan's success in handling cost cutting measures at Commonwealth Bank of Australia, where he ran its retail operations for five years till August, 2012.