The Special Adviser to President Bola Tinubu on Information and Strategy, Bayo Onanuga, has challenged former Vice-President Atiku Abubakar to explain a $500,000 payment made to his former wife, Jennifer Douglas, in 2003 amid negotiations surrounding the controversial Mambilla Hydroelectric Power Project.

Onanuga made the call in a statement on Friday, accusing Atiku of avoiding questions about the transaction while publicly criticising the Federal Government's economic policies, including its position on petrol and electricity subsidies.

The controversy stems from findings contained in the final award of an International Chamber of Commerce (ICC) arbitration tribunal in Paris over the long-running dispute involving Sunrise Power and Transmission Company Limited and the Federal Government of Nigeria.

According to the tribunal's findings, Leno Adesanya, promoter of Sunrise Power, acknowledged transferring $500,000 to Douglas on January 30, 2003, through China Castle Investments Limited, an offshore company he controlled.

Adesanya told the tribunal that the transaction was part of a foreign-exchange arrangement undertaken for Atiku and was unrelated to Sunrise Power's bid for the Mambilla project. However, the tribunal noted that the explanation was not supported by contemporaneous documents showing the underlying naira transaction, exchange rate, instructions from Atiku or his aides, or the commercial purpose of the payment.

The payment occurred less than four months before then Minister of Power and Steel, Olu Agunloye, purportedly awarded Sunrise Power a build-operate-transfer contract for the 3,960-megawatt Mambilla project.

While the tribunal considered the timing and circumstances surrounding the payment, reports of the award indicate that it did not find that Atiku personally received a bribe or directed the payment. Atiku was also not a party to the arbitration proceedings and did not testify before the tribunal.

Despite this, Onanuga said the former vice-president should publicly clarify the circumstances surrounding the transaction, particularly given his political ambitions and public criticism of the current administration.

The presidential aide also accused Atiku of attempting to shift attention from the Mambilla controversy through his recent comments on fuel and electricity subsidies.

The arbitration dispute itself involved substantial financial claims against Nigeria. The Federal Government said Sunrise Power had sought $680 million in settlement and interest, alongside a separate claim of more than $2.7 billion in compensation and interest connected to the Mambilla project.

The ICC tribunal ultimately rejected Sunrise Power's claims against Nigeria.

The renewed exchange between Onanuga and Atiku has brought fresh attention to the long-running Mambilla controversy, particularly the circumstances surrounding the $500,000 payment and its timing in relation to the power project.