The Solicitors Regulation Authority (SRA) has confirmed that it will not take any action against Hogan Lovells following a complaint made by Labour peer Lord Hain regarding the firm's investigation into allegations of South African government corruption.

After taking legal advice, the SRA has decided against opening an investigation or taking any regulatory action against the firm, after Hain this January called on the SRA to take disciplinary action over Hogan Lovells' work for South African Revenue Services (SARS) head Tom Moyane.

Moyane had instructed the firm in 2016 to investigate financial transactions that were identified as "suspicious or unusual" by South Africa's Financial Intelligence Centre, and while Hogan Lovells recommended that disciplinary action be taken against SARS deputy chief Jonas Makwakwa, Hain described the firm's findings as "an incomplete, fatally flawed whitewash of a report" and accused it of "connivance in criminality".

In a House of Lords debate, he called on the regulator 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".

An SRA spokesperson said: "We have looked into this matter in detail and taken expert legal advice. We have concluded that the issues Lord Hain has raised with us are about work carried out by solicitors that we do not regulate, and therefore the matter is outside of our jurisdiction. For that reason, we have closed the matter."

A Hogan Lovells spokesperson added: "Hogan Lovells has consistently rejected the allegations made by Lord Hain. This was a piece of work carried out in South Africa for a South African client by South African-qualified lawyers and we are pleased that the SRA, with whom we have fully cooperated, agrees with this.

"The appropriate forum for resolving any dispute is, and always has been, in South Africa with the Law Society of the Northern Provinces and we are working closely with them. In addition, the chair of our practice in that country has twice given evidence to the South African parliament and fully accounted for the work that we undertook."

Hain said he was "extremely disappointed with the outcome", and said that he would pursue "this matter of lax UK solicitor regulation" when parliament resumes in the Autumn.

Hain told the SRA: "Hogan Lovells UK have managed through a procedural body-swerve to avoid culpability because, according to the SRA, it 'does not control' Hogan Lovells SA and is linked only as 'essentially a branding exercise'. This seems to me plain legal sophistry, which brings an international law firm like Hogan Lovells into even greater disrepute, adding to their terrible reputation for whitewashing corruption and money laundering in the South African Revenue Service.

"It seems to me that the SRA is simply standing by and allowing Hogan Lovells to slip through [its] investigative loopholes, which does legal regulation in the UK no credit at all."