Neil Mitchell launched the RBS GRG Business Action Group yesterday to bring together hundreds of British businesses who believe they were wrongly forced into administration by the taxpayer-funded bank so it could profit from their assets.
The claims, which relate to the bank's controversial Global Restructuring Group (GRG), are already the focus of an investigation by the Serious Fraud Office and the police.
Now the group is preparing to pursue tens of billions of pounds in compensation in a legal case led by QCs Andrew Hunter and Lord Pannick, who has previously acted for the Queen and Max Mosley in press privacy lawsuits.
The lawyers have up to 120 days to compile enough evidence to pursue RBS for damages in a conspiracy to defraud case on behalf of all businesses allegedly damaged or destroyed by being pushed into GRG, which has been dubbed a "butcher's shop".
About 400 firms, from small and medium businesses to high street names such as HMV, are being represented by the group, with Mr Mitchell urging anyone else who became involved with GRG to get in touch.
The UK's Department For Business, Innovation & Skills estimated last August the value of compensation claims for SMEs could total £5 billion to £20bn, but it has since emerged the claim could also include large companies.
RBS chairman Sir Philip Hampton recently confirmed GRG at its peak was handling tens of thousands of British businesses with assets worth £91bn.
Mr Mitchell, a former chief executive at AIM-listed software company Torex Retail, said: "This is not just equally scandalous (to the credit crunch) but there are whispers around Gogarburn they could need another bailout on the back of this.
"That was supposed to be a last resort to turn the industry around, but here we are six years later and things are even worse. I know this case is being watched with great interest by those at the top of government.
"My hope is we can get recompense for the hundreds of businessmen and women who lost their livelihoods because businesses were improperly moved into GRG and forced into administration.
"It should also be recognition for the tens and tens of thousands who have lost their jobs as a result of RBS cuts or businesses going bust on the back of RBS decisions."
Last November, Lawrence Tomlinson, the "entrepreneur in residence" at the UK Department For Business, Innovation & Skills, accused RBS of routinely moving stable, creditworthy businesses into GRG for profiteering purposes, and of deliberately engineering defaults among SMEs and corporate borrowers by, for example, withholding critical payments.
The strategy is said to have arisen in the aftermath of the £850bn bailout in 2008 when there was pressure for the bank to return to the private sector at a profit within three to five years. This reportedly led them to pursue on short-term financial gains at the behest of the UK Government and UK Financial Investments, the vehicle for holding taxpayers' stakes in RBS and Lloyds.
An RBS spokeswoman said: "These are serious allegations that have done damage to RBS's reputation. The independent review by Clifford Chance we have commissioned will examine these.
"The most serious allegation made is RBS conducted a 'systematic' effort to profit on the back of our customers when they were in financial distress. We do not believe this is the case and no evidence has been provided for that allegation to the bank."