A parliamentary group on fairer finance has reignited its row with the Financial conduct Authority (FCA) today, comparing the watchdog to the Post Office and accusing bosses of engaging with criticism in a “disappointing, defensive and dismissive” way.

In a new report, the All-Party Parliamentary Group on Investment Fraud and Fairer Financial Service, which counts Jeremy Cobyn’s shadow Chancellor, John McDonnell, and the former chair of the Competition and Markets Authority, Lord Tyrie, among its members, said the FCA had been “unconstructive” in responding to a 350-page paper which criticised its operations in November.

“For the record, and the avoidance of any doubt I wish to politely and respectfully state that I am disappointed with the FCA’s response,” Bob Blackman, chair of the group, wrote.

The initial findings, compiled through testimony from 175 whistleblowers, former employees and current staff, painted a scathing picture of the FCA and accused it of failing consumers and forging an overly cosy relationship with the firms it regulates.

Blackman’s group has now also challenged the FCA’s claim that 85 per cent of its stakeholders are satisfied it is protecting consumers, and claimed its behaviour was reminiscent of the Post Office.

“The FCA, like the Post Office, has too many red flags. And like the Post Office the FCA’s lack of objectivity and self denial of the problem only serves to emphasise how critical the need for a resolution is,” Blackman wrote.

The Financial Conduct Authority has hit back at the latest criticism and said it had proposed a meeting with the APPG’s chairs to discuss their concerns, an offer that was not mentioned in the report.

“We recognise there are a range of views in Parliament about our objectives,” a spokesperson for the FCA said. 

“We continue to protect consumers while embracing the new secondary growth and competitiveness objective given to us by Parliament. As we set out in our recent letter to the Prime Minister, we welcome a debate and as broad a consensus as possible about the appropriate risk appetite we should work to.”