A former Nigerian oil minister cleared of taking bribes says the UK authorities destroyed her reputation in a failed prosecution that was "painful and traumatic".

Diezani Alison-Madueke said the 13-year investigation by the National Crime Agency (NCA) "could have been handled a lot differently".

Speaking exclusively to the BBC, she said: "I've not been allowed to travel. I've not been allowed to work. They destroyed my reputation and my integrity."

On Wednesday, the former minister was found not guilty at Southwark Crown Court of five counts of accepting bribes and conspiracy to commit bribery in a trial that began in January.

Alison-Madueke, 65, was Nigeria's oil minister between 2010 and 2015 and the first female president of the oil exporters' group Opec.

"When your freedom is taken away from you… it has a very deep impact upon you psychologically," she said.

"I knew that I had never done anything nefarious and I had never done any of the heinous things I was being accused of doing."

Alison-Madueke, who was first arrested in 2015, but not charged until 2023, was accused of receiving kickbacks from wealthy oil tycoons with government contracts who provided her with "a life of luxury".

The alleged bribes included £2m ($2.65m) worth of goods from Harrods, chauffeur-driven cars and the use of multi-million-pound properties in London and Buckinghamshire.

'There's a bit of blame everywhere'

But from the start of the trial in January, defence lawyers questioned the fairness of the prosecution's case, alleging that vital documents proving Alison-Madueke's innocence had gone missing in Nigeria.

She says these included boxes of receipts showing the oil tycoons had been reimbursed for payments made on her behalf.

"Those items were taken away by our intelligence forces" from her home in Abuja in 2015, she said, adding that she had no idea what happened to them.

Former Nigerian President Goodluck Jonathan, who appointed Alison-Madueke, wrote to the court stating that third parties would often pay for ministers' transport and accommodation on overseas business.

Asked who she holds responsible for the failings in the case against her, Alison-Madueke said: "There's a bit of blame everywhere.

"The Nigerian authorities need to look into the processes and practices that they deploy in these cases."

The BBC has asked the Nigerian government for comment.

As for the NCA, she said: "The long arm of the law when you go into other countries, particularly in politically motivated cases, needs to have a lot more sensitivity."

She believes the agency went after her because she was "low-hanging fruit", ignoring the work she says she did to counter corruption in the oil industry and the fact she had made powerful enemies in Nigeria, Africa's largest oil producer.

"I was the first female to enter this sort of position as petroleum minister and as head of Opec in a very misogynistic society."

The NCA should have "taken a step back and looked with a little more depth at the truth of the situation on the ground", she said.

An NCA spokesperson told the BBC the agency had "conducted a long-running, in depth and complex investigation which was regularly reviewed throughout its duration by CPS [Crown Prosecution Service] and the investigators".

The spokesperson added that the NCA had "worked closely with international partners and, as in all cases, this investigation was carried out with impartiality".

"A comprehensive file of evidence was presented to the CPS who authorised charges and we respect the decision of the jury in court."

Alison-Madueke's older brother Doye Agamas, 69, an archbishop in a Pentecostal church in Manchester was also acquitted of conspiracy to commit bribery.

Oil industry executive Olatimbo Ayinde, 54, was found not guilty of bribery and bribery of a foreign public official. She had faced prosecution despite being an informant in an anti-corruption investigation by the Nigerian authorities.

In 2023 the US Justice Department recovered $53m (£40m) worth of assets seized from two of the oil tycoons named in this trial.

In a statement at the time a department spokesperson said "Alison-Madueke used her influence to steer lucrative oil contracts" to companies owned by the men.

On this point, Alison-Madueke told the BBC: "I was never given the opportunity to fight that because I wasn't even charged" and that the contracts were subject to "the exact due process that they are supposed to go through."

Nigeria's anti-graft agency, the Economic and Financial Crimes Commission (EFCC) says it also recovered about $153m and more than 80 properties from the politician in 2022.

Asked about this, she replied: "The assets that have been forfeited were not actually traced directly to me... I don't know what has happened to these matters at all. It's now that I'll have the freedom to find out what exactly has gone on there."