Oil tycoons Igho Sanomi and Kevin Okyere deny bribing former Nigerian oil minister Diezani Alison-Madueke

Igho Sanomi and Kevin Okyere have used UK investigators' files to push back at the bribery case against former Nigerian oil minister Diezani Alison-Madueke. The court heard statements from the two oil tycoons at Southwark Crown Court on Tuesday, with both men denying that money or goods they directed her way amounted to bribes.

Sanomi, the Nigerian oil tycoon behind Taleveras Group, told the National Crime Agency in June 2017 that "foreign currency exchange [was] difficult in Nigeria" and that he had "obtained items on Mrs Alison-Madueke's behalf in London" on the understanding everything would be reimbursed. He also told investigators his companies "always won their contracts fairly bidding against other competitors" and that the former minister was never improperly involved in any allocation to him.

Okyere, the Ghanaian businessman behind several oil and gas firms, gave a written statement in June 2016 about a 2014 encounter at Peter Jones in London. He said he had paid £3,900 for items Alison-Madueke was buying after running into her at the till and noticing she was short of cash. She later reimbursed him at his Abuja office, he said. The bribery allegation was, in his words, "completely untrue".

Prosecutors have not charged either Sanomi or Okyere in this case, and neither has appeared in person in court.

The accounts came on a day that also featured a statement from former Nigerian president Goodluck Jonathan, who appointed Alison-Madueke as oil minister in 2010. Jonathan said it was not unusual for third parties to make payments on behalf of ministers on official business, with the in-kind assistance "recorded and reimbursed where applicable". He also said he had approved her use of private jets on some foreign trips.

Alison-Madueke, 65, denies five counts of accepting bribes and one count of conspiracy to commit bribery. The prosecution alleges that oil industry insiders bankrolled what it has called a "life of luxury" for her, including stays at multimillion-pound homes, chauffeur-driven cars and a November 2013 visit to a London antiques dealer where £170,000 changed hands. She told the court most of the antiques were not for her, adding "I don't think anyone would risk their career for furniture and handbags." She has insisted she repaid any costs of services arranged during her official trips.

Her brother Doye Agama, a former archbishop, and oil industry executive Olatimbo Ayinde also face charges and deny them. The trial continues.