The Royal Bank of Scotland (RBS) has appointed Clifford Chance (CC) to conduct an inquiry into the its lending to small and medium sized enterprises (SME) after the bank was slammed in two separate reports.

One of those reports, commissioned by RBS and led by former Bank of England deputy governor Sir Andrew Large, criticised the treatment of some SME customers, and said the bank must confront some "serious allegations" by a number of firms.

In a letter to Sir Andrew, RBS group chief executive Ross McEwan said CC would investigate the matter and would report back in February 2014.

RBS will be hoping CC's report can pre-empt a further investigation by the Financial Conduct Authority (FCA), which was last week presented with a dossier by Business Secretary Vince Cable, which alleges the bank deliberately put good businesses into default so it could maximise profit.

"To ensure our customers can have full confidence in our commitment to them I have asked the law firm, Clifford Chance, to conduct an inquiry into this matter, reporting back to me in the New Year," said McEwan.

"It is important that we get this right, especially as our regulators want the bank to remove problem loans more quickly."

CC declined to comment on the instruction. Last year, the firm acted for the bank on matters resulting from the Libor scandal, for which the bank was fined £390m by UK and US regulators.

Last year, CC joined around 60 firms on RBS's scaled down UK and group panel, following a review which saw 40% of advisers trimmed.