Labour peer Lord Peter Hain has called on the Solicitors Regulation Authority (SRA) to withdraw Hogan Lovells' authorisation to practise for producing a "fatally flawed whitewash of a report" into allegations of South African government corruption.

In a House of Lords debate on the Sanctions and Anti-Money Laundering Bill, the veteran anti-apartheid campaigner issued a strongly worded condemnation of the firm's work for the South African Revenue Services (SARS), accusing it of having walked into a "web of corruption and cronyism for a fat fee", and being guilty of "connivance in criminality".

He confirmed that he has asked the SRA to "withdraw Hogan Lovells' authorisation as a recognised body", and to "examine what other disciplinary action can be taken against its leading partners, including withdrawing their permission to practise as solicitors".

The firm's involvement in the scandal dates back to September 2016, when it was instructed by SARS head Tom Moyane – who Hain describes as one of "the most notorious perpetrators of state capture in South Africa" – to investigate financial transactions involving SARS deputy chief Jonas Makwakwa and employee Kelly Ann Elskie.

South Africa's Financial Intelligence Centre had identified the transactions – which saw about £200,000 paid into their accounts over a six-year period – as "suspicious or unusual".

Lord Hain states that Hogan Lovells was appointed to conduct an independent investigation and "recommend and independently facilitate necessary disciplinary action".

While South African chairman and employment partner Lavery Modise recommended that disciplinary action be taken against Makwakwa for "non-disclosure of external business interests and contravention of his suspension conditions", Lord Hain described the firm's' findings as "an incomplete, fatally flawed whitewash of a report, which ultimately cleared Makwakwa".

He characterised the firm as "either a willingly gullible or malevolent accomplice" and accused it of "complicity in propping up state capture, corruption, cronyism and money laundering in South Africa".

In a letter sent to the SRA last week and seen by Legal Week, Lord Hain accuses the firm of having "enabled a corrupt money-launderer to be returned to his post as second-in-command of the critically important SARS".

His letter continues: "It is totally unnacceptable for a British firm regulated by the SRA to behave in this fashion and I trust that SRA disciplinary action will follow."

In a statement provided to Legal Week prior to Lord Hain's comments this afternoon, Hogan Lovells defended its work for SARS and expressed disappointment that he had not contacted the firm about the scope of its work for the organisation.

A spokesperson said: "Lord Hain's unfounded accusations reflect a lack of understanding of the work we were asked to carry out for the South African Revenue Service. We are disappointed that he ignored the evidence provided by us to him and the other committee members earlier today. He did not contact us in advance of making his statement to the House of Lords and instead appears to have relied on inaccurate and discredited press reports in South Africa.

"We have fully reported the details of our engagement with SARS to the independent South African Parliament Standing Committee on Finance and we are very confident in its accuracy and probity. Anyone who wants to take the time to understand our limited role in this matter can very easily read about it on the Parliament's website or our own.

"We have a fundamental duty to uphold the rule of law with integrity and professionalism, and have been strong advocates of that in South Africa. If Lord Hain does have evidence of corruption, then that should be reported to the appropriate authorities in South Africa. We look forward to working closely with the SRA on any complaint made to them by Lord Hain."