Two powerful committees of MPs have launched separate inquiries into protections for small businesses in the wake of the RBS Global Restructuring Group (GRG) scandal and the collapse of outsourcing giant Carillion.

The Treasury select committee said its inquiry would try to learn the lessons from GRG – a turnaround unit of taxpayer-controlled RBS that mistreated more than 90pc of struggling firms transferred into it between 2008 and 2013.

Meanwhile the business select committee said its own investigation would focus on Government support for small businesses and the unfair treatment of small firms by large firms highlighted by Carillion’s demise.

On Tuesday RBS’s top bosses – chief executive Ross McEwan and chairman Sir Howard Davies – admitted multiple failings at GRG in a bruising grilling by MPs on the Treasury committee.

Sir Howard admitted some behaviour by staff within GRG was “the stuff of nightmares”, including an internal memo unearthed that encouraged managers to give customers in financial distress enough rope to “hang themselves”.

Mr McEwan said the bank would not stand in the way if Britain’s financial watchdog the Financial Conduct Authority (FCA) decided to publish its report into GRG in full.

Within hours the FCA said it would do so, although full publication may take months as it tries to obtain consent from individuals named within it – a process known as ‘Maxwellisation’.

An earlier summary of the report found “widespread inappropriate treatment” of firms by GRG, with only one in ten companies returning to normal banking.

Nicky Morgan, who chairs the Treasury committee, said the GRG case had “undermined the trust of small firms in banks”.

“Little has changed since GRG to prevent similar mistreatment happening again, nor to guarantee victims access to fair and reasonable redress,” she added.

The Treasury committee will focus on lessons to be learned from GRG and the state of the finance market for small companies, including whether there is adequate competition.

Rachel Reeves, who chairs the BEIS committee, said Carillion’s failure had shown the stresses placed on small business finances.

“Deliberate supply chain bullying can be devastating for business owners and contributes to thousands of business deaths each year. We want to hear if the Government could be doing more to stop this,” she said.

The business inquiry will also look into small business productivity, training and late payment.

Separately Ms Morgan warned today of the risk to Britain’s cash machine network posed by a proposed cut to the fee banks receive every time an ATM is used.

Link, which oversees ATMs, confirmed it would reduce the so-called interchange fee collected by operators from 25p to 20p per withdrawal, phased over four years.

Ms Morgan urged watchdog the Payment Systems Regulator to ensure customers do not lose out on access to ATMs.

She said: “Any significant reduction in free access to cash would be an unacceptable outcome.”

Link said it had brought in protections following a consultation, including ensuring all ATMs more than a kilometre apart would be exempt from the reduction, while an enhanced subsidy of 30p would be paid to ensure free ATMs in some rural areas.