The attorney general has launched an independent review after judges severely criticised Britain’s main anti-corruption agency and overturned the conviction of a businessman because of its misconduct.

Three court of appeal judges concluded that the Serious Fraud Office’s failure to disclose vital evidence had unfairly led to the businessman being jailed for bribery.

The judges said that the SFO had withheld “embarrassing” evidence that would have detailed its “wholly inappropriate” dealings with a private investigator, for which the agency had already been criticised.

After the ruling the office of the attorney general, Suella Braverman, issued a statement saying she was “deeply concerned about the findings in the judgment” and would discuss its “implications” with the director of the Serious Fraud Office, Lisa Osofsky.

“The attorney general has today commissioned an independent review of the issues highlighted including disclosure failings at the Serious Fraud Office,” the statement said.

The SFO had already been compelled to set up an inquiry into its dealings with the investigator, David Tinsley, after criticism last year by the judge who presided over the original trial of the businessman, Ziad Akle.

However, the Attorney General’s Office said that Braverman’s review would report directly to her and would be independent of the SFO. Braverman’s office is responsible for overseeing the SFO.

During the original trial, at Southwark crown court, the judge, Martin Beddoe, rebuked Osofsky and the SFO over “flattering” text messages she received from Tinsley, who was seeking to secure more favourable sentences for other businessmen involved in the case.

Beddoe said that Osofsky and other senior SFO figures should not have had any contact with the investigator, who had no recognised legal role in the case.

In Friday’s ruling, the three appeal court judges, Lord Justice Holroyde, Mr Justice Jeremy Baker and Mr Justice Jay, cleared Akle, who had been jailed for five years after being convicted of conspiracy to make corrupt payments to Iraqi officials.

The judges said the SFO’s failure to hand over key documents had “significantly handicapped” Akle’s defence at his original trial last year, and that “in consequence, through no fault of the judge, Akle did not have a fair trial”.

Akle had been one of four businessmen convicted for his role in a corrupt scheme run by a consultancy, Unaoil, that paid huge bribes around the world for years.

The judges detailed how Tinsley, who runs an American private investigations firm, had been hired by the Ahsani family, which owned the Unaoil consultancy. They described how Tinsley had tried to persuade Akle and other junior employees to plead guilty, apparently in exchange for lenient sentences for the Ahsanis.

Akle’s lawyers argued that Tinsley’s extensive contact with senior SFO prosecutors had undermined his chance to have a fair trial, accusing the agency of withholding documents that recorded that contact.

The three judges said: “That failure was particularly regrettable given that some of the documents had a clear potential to embarrass the SFO in their prosecution of this case. We do not suggest that any individual official of the SFO deliberately sought to cover anything up.”

However, they also said that the SFO had not properly explained how Kevin Davis, its chief investigator, had deleted data on his mobile phone that logged his interactions with Tinsley.

“The explanation which has been put forward is that Davis repeatedly entered an incorrect code, which caused data to be wiped from his phone,” they wrote.

“If that explanation is correct, it appears to have been the second time in less than a year that Davis had caused a mobile phone to be wiped and in need of rebuilding.

“Moreover, it would have involved his not only entering the wrong password five times, but doing so despite a specific warning on the phone to contact the service desk.”

Sue Hawley, the executive director of the campaign group Spotlight on Corruption, said the overturning of the conviction was “a devastating setback for the SFO”.

“The finding of serious disclosure failures to prevent embarrassing material about the agency’s handling of the case must lead to an immediate independent and judge-led review of what went wrong, and who is responsible,” she said.

Akle said: “This has been a difficult four-and-a-half years for myself and my family.” His lawyer, Jo Dimmock, said: “This case became about the conduct of the SFO. By acting in the way it did it undermined the whole justice system.”

An SFO spokesperson said: “We note today’s decision by the court of appeal and are currently reviewing the judgment.” They added it would not challenge the judges’ ruling not to have a retrial of Akle.