A union today pressed Royal Bank of Scotland to explain its use of contractors after a recruitment agency mistakenly emailed the details of hefty pay packets for thousands of temporary staff.
Unite has expressed "serious concerns" over the revelations, inadvertently exposed by an employee of Hays, which are understood to show temporary staff receiving up to £2,000 a day - equivalent to £500,000 a year.
Some 3,000 contractors' names and billing rates were mistakenly attached to an email sent from Hays to 800 RBS staff which was supposed to remind managers to complete timesheets before the bank holiday weekend.
The insight into contractors' wages is likely to provoke outrage as RBS is not only 83% owned by the state but in the process of cutting thousands of permanent staff jobs.
David Fleming, Unite national officer, said: "It is wholly inappropriate that RBS, backed by taxpayers, appears to be throwing money at thousands of contractors."
RBS said it was "disappointed" by the incident, while Hays said it had apologised to the bank for the error and has launched an investigation.
RBS said this month around 2,000 jobs would go at its investment banking arm in the next 12 to 18 months as it unveiled a half-year loss of £794 million.
Furthermore, the bank's share price has fallen to 20p - less than half the 50p price tag paid by the Government for its stake.
It is understood temporary staff work in divisions ranging from human resources to risk management, while the highest-earning contractors have specialist accounting, financial and IT expertise.
Mr Fleming said contractors should not be used as a short term fix and the bank should focus on investing in staff.
He said: "Unite the union has serious concerns about the widespread use of highly-paid staff on short term contracts at a time when RBS continues to cut large numbers of staff.
"We have expressed to the bank our unhappiness that thousands of permanent staff are being sacked when contractor staff continue to work in other areas of the bank."
Hays said it recognised the correct treatment of data was "of the utmost importance".
It said: "Hays has launched an internal investigation to understand fully the circumstances that led to this unauthorised release of information and to review its procedures to ensure it cannot happen again."
A statement from RBS said: "We are extremely disappointed that confidential personnel data has been shared by one of our suppliers.
"This is unacceptable and we are taking action to address this issue. No customer information has been compromised."