The Court of Appeal in London told the UK Serious Fraud Office to hand over private texts and other evidence of contacts between its director and a US fixer for bribery suspects after a judge said they might have been “improper”.

On Thursday, judges told the anti-graft agency it had to reveal the extent of its relations with Miami-based agent David Tinsley. They were speaking at the start of an appeal hearing by Ziad Akle, a former executive at oil and gas consultancy Unaoil, who was convicted and jailed for bribery offences last year.

The ruling adds to pressure on the agency and marks the second time it has been told to review the Tinsley contacts. The Unaoil trial judge criticised SFO director Lisa Osofsky last year and suggested she had fallen for the fixer’s “flattery”.

Akle has accused Osofsky of encouraging Tinsley, a former US Drug Enforcement Administration official who represented Unaoil’s founding Ahsani family, to induce him to plead guilty while trying to secure a lenient deal for his clients, who were also suspected of bribery.

Akle did not plead guilty but claims the SFO’s conduct leading to his conviction was wrongful.

On Thursday Akle’s lawyer, Adrian Darbishire QC, asked the court to compel the agency to hand over documentary evidence revealing what occurred between senior SFO officials and Tinsley, in order to be able to proceed with his appeal.

The Court of Appeal told the SFO to explain the “manner and circumstances in which contact was initially made between David Tinsley and the SFO”. It also ordered the agency to hand over all relevant contacts with him and piece together any details of unrecorded meetings by interviewing senior members of staff.

On Thursday, Mr Justice Jay said there appeared to be evidence that the contacts were “improper”. “What’s being alleged here is very serious abuses of power by the SFO going right to the very top,” he said.

Darbishire told the court on Thursday that Tinsley had called Osofsky “my new most favourite person” in a text message. He said there appeared to be no record in Osofsky’s office diaries of any of the six meetings with Tinsley that Akle believes took place.

The absence could “only sensibly be part of or the consequence of a deliberate policy,” he said. “It cannot be coincidence or chance that meetings between these two entities . . . just happened to be overlooked in terms of record keeping.” Any attempt to deliberately deprive the defence of material was “a perversion of justice”.

The SFO argued on Thursday that Tinsley may have inflated the number of contacts he had had with the director, and said the requested disclosure would not aid Akle’s case.

Michael Brompton QC, representing, the SFO, said Osofsky had conducted only two “substantive” meetings with Tinsley but conceded there may have been “chance encounters” or instances where they had “met in the corridor”.

Lord Justice Tim Holroyde interjected to ask why Tinsley was ever at the SFO. “Why was he in the corridor? In the usual run of things one wouldn’t expect to find an American fixer . . . roaming the corridors of the SFO,” he said.

Darbishire said Tinsley had approached Osofsky in 2018 and proceeded to cultivate a relationship with the agency. He said the SFO “knew about and encouraged” his attempts to engage with Akle and another defendant behind the backs of their lawyers. Darbishire said Tinsley’s role “seems to have been to get the Ahsanis out of the hands of the SFO” in order to plead in proceedings in the US and appeared to have succeeded.

Cyrus and Saman Ahsani both pleaded guilty to bribery in the US in 2019 and are awaiting sentencing. Darbishire said it appeared unlikely that they would go to prison.

Akle’s appeal was adjourned, and will take place at a later date. Another defendant Paul Bond, formerly a senior sales manager with Unaoil client SBM Offshore, is also appealing against his sentence.