Bosses at Royal Bank of Scotland believe the lender will be cleared of the most serious allegations levelled at its Global Restructuring Group in a matter of weeks but fear a legal battle over its 2008 cash call could last until 2021.

Senior managers at RBS are understood to be confident the City watchdog will dismiss claims the bank’s controversial Global Restructuring Group (GRG) deliberately pushed small businesses into bankruptcy during the financial crisis so that their assets could be acquired at knock-down prices.

The Financial Conduct Authority (FCA) has been urged to disclose the findings of an investigation. RBS believes the FCA will reveal its conclusions in “weeks not months” and that they will show the most damaging allegations against GRG are unfounded.Putting an end to the controversy over GRG would be a huge boost for RBS. It is one of a number of historical misconduct issues casting a shadow over the bank. Another is a £4bn legal battle with investors who claim they were misled into backing a rescue rights issue by RBS in 2008.

It is understood RBS’s management believes that if the lawsuit is not settled before it reaches court in March, it has the potential to drag on for four to five years. That means the case may not be resolved until 13 years after the cash call at the heart of the dispute.