PwC has been appointed by RBS to lead an independent investigation into the major IT failure that left millions of its customers in June without access to their accounts.

PwC was unable to confirm the exact nature of the investigation, but is likely to look into the management failings.

It follows in the wake of the Financial Services Authority's (FSA) recent request that the bank conduct a 'separate full review' into what went wrong that led to weeks of chaos for account holders at RBS and its sister banks, NatWest and Ulster Bank.

RBS - the publicly-owned lender has admitted that the cause of the computer meltdown stemmed from a flawed software upgrade to its overnight payments systems.

The regulator has insisted on the investigation in a bid to discover what steps the bank - which has around 17m UK business and personal accounts - has taken to ensure such a major failure will not be repeated.

Just last week, RBS was slammed for offering just £20 compensation to hundreds of thousands of Ulster Bank customers denied access to their money for several weeks.

RBS has already put aside £125m to compensate customers affected by the IT failure. The bank's chief executive also said that he would forgo any bonus for 2012 to make amends.

Legal outfit, Clifford Chance, has been undergoing its own investigation on behalf of RBS management, and initial findings are reported to intimate that both the bank and its external software supplier were to blame for the computer glitch.

The FSA is understood to have asked all UK high street banks to reveal their contingency plans should similar IT system problems occur.