Labour has insisted there is no justification for a new sell-off of RBS shares after reports the Government is set to offload part of its stake in the bank.
Shadow chancellor John McDonnell said such a decision would result in a big loss for taxpayers who own 72% of the bank.
Mr McDonnell said: "There is no economic justification for a further sell-off of RBS shares and it beggars belief that this Government is considering selling shares at an even bigger loss to the taxpayer than the £1 billion George Osborne managed.
"All further sales of RBS shares should be halted, and the bank reorganised under public control to help provide the patient, long-term investment capital that businesses across the country so urgently need."
The comments come as RBS executives are expected to face a barrage of questions from shareholders over dividends, branch closures and re-privatisation at the lender's annual meeting this week.
The Government had been expected to sell £15 billion worth of shares by 2023, around two-thirds of its stake.
However, it is facing a near-£26.2 billion loss on its holding, with the lender's shares languishing well below the average 502p share price paid during the 2008 and 2009 bailout, at around 292p.