London (AFP) - Former OPEC president Diezani Alison-Madueke has been charged with bribery offences relating to her time as Nigeria's oil minister, the UK National Crime Agency said on Tuesday.

Alison-Madueke has been on bail since first being arrested in London in October 2015. She will appear in court in the British capital on October 2, the NCA said.

Soon after her arrest, her family's lawyer told AFP she would strongly contest corruption allegations that have dogged her during and after her time in former president Goodluck Jonathan's government.

She has been linked to a string of money laundering, bribery and asset recovery cases in Nigeria, as well as in Italy and the United States.

In an interview with a Nigerian newspaper in November 2015, she was quoted as saying: "I challenge anyone to come forward with facts showing that I stole government or public money.

"I've never stolen Nigeria's money."

Alison-Madueke, who was in office from 2010 to 2015, was the first woman to be oil minister in Nigeria and the first female president of the global oil cartel OPEC.

The head of the NCA's international corruption unit, Andy Kelly, said: "We suspect Diezani Alison-Madueke abused her power in Nigeria and accepted financial rewards for awarding multi-million-pound contracts."

The NCA said Alison-Madueke allegedly benefitted from at least £100,000 ($127,000) in cash, chauffeur-driven cars, flights on private jets, luxury holidays for her family and the use of multiple London properties. 

The charges also detail financial rewards including furniture, renovation work and staff for the properties, payment of private school fees and gifts from top designer shops such as Cartier jewellery and Louis Vuitton goods. 

"Bribery is a pervasive form of corruption, which enables serious criminality and can have devastating consequences for developing countries," Kelly said.

"These charges are a milestone in what has been a thorough and complex international investigation," he added.

Prominent

Alison-Madueke has been living in the upmarket St John's Wood area of north London since she was first arrested and has undergone chemotherapy for breast cancer, according to her family.

At the time of her arrest, the NCA said only that it had detained five people in London on suspicion of international corruption, without naming those held.

The Nigerian government of Jonathan's successor, Muhammadu Buhari, later confirmed Alison-Madueke's arrest and said its law enforcement agencies were cooperating with their British counterparts.

Soon after taking office, former army general Buhari began a drive to root out endemic corruption and end impunity in Africa's most populous nation.

That included reforming the notoriously opaque Nigerian National Petroleum Corporation (NNPC), which Alison-Madueke oversaw.

But Buhari -- who said "mind-boggling" sums had been "looted" from the country over decades -- was accused of largely targeting his political opponents and those from the previous administration.

The NCA said that assets worth millions of pounds in relation to the case have been frozen as part of the long-running investigation.

Earlier this year, the agency, which targets international and serious and organised crime, said it provided evidence to US prosectors allowing them to recover assets totalling $53.1 million linked to Alison-Madueke's alleged corruption.

They included luxury real estate in California and New York, as well as a 65-metre superyacht, the Galactica Star, the US Department of Justice announced on March 27. 

Alison-Madueke, born to a well-off family in the oil city of Port Harcourt in 1960, studied architecture in Britain and the United States before joining oil major Shell's Nigerian subsidiary.

In politics she held three major positions in government -- first as transport minister in 2007 under president Umaru Yar'Adua, then minister of mines and steel development.

When Jonathan -- who was also from southern Bayelsa state -- took over after the death of Yar'Adua, he appointed her minister of petroleum resources in April 2010, making her a powerful figure.