South Africa's official opposition, the Democratic Alliance (DA) on Wednesday told the High Court in Pretoria that the R30.1-million pension granted to former Eskom CEO Brian Molefe was unlawful.

"He told the whole nation and the minister [Public Enterprises ... Minister Lynne Brown] that he was departing because there was a cloud over his head. He didn't tell anyone that behind the scenes he was trying to get this vast amount of money," Advocate Paul Kennedy SC argued on behalf of the DA.

The high profile case was heard on Wednesday before a full bench of high court judges - Judge Elias Matojane, Judge Hans Fabricius and Judge Segopotje Mphahlele.

Kennedy told the packed court that Molefe resigned and then attempted to convert his resignation to an early retirement package - pocketing the more than R30-million.

The DA requested the superior court to give a declaratory order, forcing Molefe to pay back his pension payout. Kennedy submitted that the Pension Fund should calculate the actual amount to be reimbursed by Molefe.

"He has acknowledged that he was not entitled to get any money under early retirement," said Kennedy.

Mileage was in court, listening attentively as the case kicked off on Wednesday morning. The matter has been set down to be heard for three days, starting on Wednesday.

Molefe was taken to court by Solidarity, and DA, which wants his R30.1-million pension payout in 2017 ruled unlawful and set aside.