A former prosecutor at the uks anti-fraud agency has claimed he was fired following a plan hatched between the us department of justice and a prime corruption suspect that was a naked and transparent attempt to get me out of the way.

Tom martin, in charge of the serious fraud offices high-profile corruption investigation into monaco-based oil and gas consultancy unaoil, was sacked in december 2018, 19 months after allegedly swearing at an fbi agent in a pub.

The lawyer is suing the sfo for wrongful and unfair dismissal in a london employment tribunal, alleging the incident was not the true reason for his sacking.

The case is the latest development in the multimillion dollar unaoil probe that has resulted in three convictions in the uk and spawned a string of investigations into other companies around the world

At the start of the tribunal on tuesday, mr martins lawyer, jason galbraith-marten qc, said his client had been sacked because of a row between the sfoand doj over which agency would secure the prosecution of saman ahsani, a member of unaoils founding family.

In legal arguments filed with the tribunal, mr martin claimed the sfo, which was keen to rebuild relations with its rival agency, failed to properly investigate allegations made against him.

The sfo investigated the pub incident in 2017 following an informal complaint but took no further action.

Mr martin, was suspended in july 2018, a day after a series of complaints were submitted by the doj on behalf of mr ahsani. the us agency had also filed its own complaints about mr martin, which included the pub incident.

In its tribunal submission, the sfo said a formal investigation following the july complaint concluded the pub incident constituted unacceptable abuse on a personal level and amounted to gross misconduct, adding mr martin also lied about the event.

The complaints landed at the height of a bitter row between us and uk law enforcement over mr martins attempt to extradite mr ahsani from rome. this was ultimately thwarted when he co-operated with the doj.

Mr galbraith-marten said on tuesday there was a conspiracy between the department of justice and the ahsanis to file a complaint that would destabilise the sfos case and smooth the way for mr ahsani to plead in the us.

In submissions made to the sfo's internal investigation and a subsequentappeal in 2018 read to the tribunal, mr martin said the complaints were motivated by a joint desire to see me removed as case controller and were a naked and transparent attempt to get me out of the way.

In its written arguments to the tribunal, the sfo admitted for the first time to the poor state of its relations with the doj during 2018. interim director mark thompson had travelled to the us in order to seek to repair the relationship with the us authorities, the agency said.

Mr martin alleges that the pub incident which took place in 2016 was not serious enough to warrant his dismissal.

The sfos decision to sack him was not a neutral act, he said, addingthe agency had allegedly disclosed confidential information to the doj about his suspension. it took place at the same time as the agency was attempting to patch up relations with its fellow agency.

But giving evidence on tuesday tony osbaldiston, a non-executive director of the sfo who conducted the agencys internal investigation into mr martins behaviour in 2018, called his conspiracy allegations fanciful.

He said: his behaviour stands on its own two feet, and even if it was raised [by ahsanis lawyer and the doj] in the hope it might remove him from the scene it was still unacceptable behaviour.

According to the sfos legal arguments, three witnesses reported hearing mr martin call the fbi agent a cunt, four people reported hearing him describe the agent as a spy and five confirmed they heard him use the word quisling.

The case continues.