Koeberg power station near Cape Town. (Photo: Bruce Sutherland)

South Africa's controversial push to build a fleet of new nuclear plants suffered a setback on Wednesday after the High Court set aside the procurement process and a pre-agreement with Russia.

There have been persistent rumours that President Zuma and his business friends the Gupta brothers are in for a sizeable kickback of the project and have pushed for its implementation even though some economists have said the country's ailing economy cannot afford to build new nuclear plants, whose costs are estimated around 1 trillion rand ($76 billion).

South Africa, which has the continent's only nuclear power station, has asked power utility Eskom to procure an additional 9 600 megawatts (MW) of new capacity as it tries to diversify its energy mix away from ageing coal-fired plants.

Judge Lee Bozalek said any request for proposal or request for information to kickstart the procurement process was set aside as well as a deal to cooperate with Russia on the plan.

"The minister's decision on or about 10 June 2015 to table the Russian IGA before parliament… is unconstitutional and unlawful and it is reviewed and set aside," he said.

In late 2014, then energy minister Tina Joemat-Pettersson signed an intergovernmental agreement (IGA) with Russia's state nuclear company Rosatom, saying the countries would cooperate in reactors with total installed capacity of up to 9 600 MW.

It was not immediately clear whether the government would appeal the ruling. Both Eskom and the Department of Energy declined to comment.

The court ruling is a victory for NGOs and other critics of the plan. The High Court in Cape Town ruled that the administration had failed to allow adequate public consultation for preliminary agreements with Russia, South Korea and the United States to build eight reactors.

Environmental groups led by Earthlife Africa had challenged the plan in court, saying the government had not properly evaluated the true financial costs and environmental impact.

Agreements with two other countries, China and France, were not affected by the ruling.

South Africa has been struggling for years to meet growing electricity demand, leading to rolling blackouts that have held back economic growth. The country relies mainly on coal-fired power plants, with one nuclear plant.

The government says the new reactors would supply more than five times current nuclear output. The plan was announced in 2010. But credit agencies cited doubts about the affordability of the plan when downgrading South Africa's credit ratings to "junk" status in recent months.

"We are highly vindicated by the today's judgement. The rule of law has prevailed in this long and complex battle," said Earthlife Africa spokeswoman Makoma Lekalakala.