South African opposition calls for debate on "witch-hunt"

South Africa's main opposition party called on Thursday for a parliamentary debate into what it called a "witch-hunt" against Finance Minister Pravin Gordhan, who is under police investigation over a suspected spy unit at the tax service.

Gordhan said on Wednesday he had no legal obligation to obey a police summons linked to an investigation into whether he used the South African Revenue Service (SARS) to spy on politicians including President Jacob Zuma.

News of Gordhan's summons compounded investors' worries about a power struggle between Zuma and Gordhan as Africa's most industrialised economy teeters near a recession and credit rating agencies consider downgrading it to "junk" by year-end.

The rand has weakened around 5 percent since the news of the police summons emerged on Tuesday.

"I have today submitted an urgent request to the Speaker of the National Assembly ... on the Zuma-mandated witch-hunt against sitting Finance Minister Pravin Gordhan," Democratic Alliance leader Mmusi Maimane said in a statement.

Political activists protested outside the offices of the Hawks, the elite police unit that is investigating Gordhan, on Thursday in solidarity with the finance minister.

Analysts have said since February, when he was first asked questions by the Hawks about the unit he set up while at SARS, Gordhan has been a target of political pressure from a faction allied to Zuma.

Hawks spokesman Hangwani Mulaudzi declined to comment.

A former finance minister, Trevor Manuel, said on Wednesday the economy would be "destroyed" if Zuma fired Gordhan, after he changed finance ministers twice in one week in December.

Investors and rating agencies back Gordhan's plans to rein in government spending in an economy that has been forecast by the central bank to grow at zero percent this year.

A Zuma-backed plan to build a fleet of nuclear power plants, at a cost of as much as $60 billion, has been a cause of tension with the Treasury for months and is likely adding to pressure on Gordhan's position, analysts say.