Financial Conduct Authority
Labour and the Lib Dems have condemned the chancellor's plan to weaken regulations introduced after the financial crash.
The government is cracking down amid concerns the schemes are driving debt.
In a landmark case on Friday the Supreme Court ruled that insurers must pay out £1.2 billion to some 370,000 businesses.
The FCA has said its legal action is the "quickest route to clarity". Small businesses have warned it may not be fast enough.
'This was too little, too late.'
Financial Conduct Authority disclosed probe in letter to Labour MP Frank Field.
'Let Customers Hang Themselves': Secret RBS Memo Sent In The Wake Of The Financial Crash Made Public
"It was a step by step guide to fleece RBS customers."
The Labour MP will call for a law change this week in Parliament