The Serious Fraud Office (SFO) has suspended the lawyer in charge of its investigation into alleged bribery and corruption at oil services company Unaoil.

An SFO spokesperson confirmed that Tom Martin, who joined the SFO in 2012 and was serving as case controller on the high-profile investigation, has been suspended pending an investigation into his conduct. The SFO declined to comment further.

Martin's suspension comes weeks before incoming SFO director Lisa Osofsky is due to take up her post in September.

Prior to joining the SFO, Martin was a senior lawyer and alternative executive counsel at the Financial Reporting Council (FRC). While at the SFO, he led the investigation and successful prosecution of Sweett Group in 2016.

The SFO confirmed in July 2016 that it was "conducting a criminal investigation into the activities of Unaoil, its officers, its employees and its agents" over suspected offences of bribery, corruption and money laundering. The investigation is ongoing.

So far, four individuals have been charged with conspiracy to make corrupt payments, including Unaoil's Iraq partner Basil Al Jarah, Unaoil's territory manager for Iraq Ziad Akle, Paul Bond and Stephen Whiteley. Whiteley is a former vice-president and Bond a former senior sales manager with Dutch-based oil and gas company SBM Offshore.

The Monaco-based oil consultant – which offers companies local knowledge on workforce, engineering and construction issues – drafted in Clifford Chance to advise it during the investigation. The firm's team was led by London white-collar and regulatory partner Luke Tolaini alongside investigations director Zoe Osborne.

The allegations against Unaoil first came to light in March 2016 following an investigation by Huffington Post and Australian broadsheet The Age, based on leaked documents.

The paper reported that between 2002 and 2012, Unaoil bribed officials to help its clients win contracts across the globe.