South Africa's largest trade union has joined calls for President Jacob Zuma to step down.

While the Congress of South African Trade Unions (Cosatu) have vigorously defended Zuma in the past, they now say they have lost confidence in him after his dismissal of Pravin Gordhan, the finance minister.

The sacking in the early hours of Friday has had serious consequences for the country's economy and deepened the rift within the ruling African National Congress (ANC).

"The time has arrived for him [Zuma] to step down and allow the country to be led forward by a new collective at a government level," Cosatu said in a statement.

South Africa's credit rating downgraded to 'junk' status

Cosatu is in an alliance with the ANC and the South African Communist Party, which had already called for Zuma’s resignation last Friday.

But ultimately Zuma's fate rests with the ANC.

Since Gordhan’s dismissal, a leading financial agency, S&P Global Ratings, has downgraded South Africa's credit rating to "junk" status. They blame political uncertainty and the abrupt sacking of Gordhan.

This has added pressure on the ANC's top officials, many of whom remain divided on Zuma.

OPINION: Even if Zuma goes, South Africa will remain divided

Zuma himself, in his first public comments since he dismissed Gordhan, said that fiscal policies would be unchanged and that people should remain calm.

In an effort to reassure markets, Zuma said he expected the addition of "many young ministers" to "add renewed energy into cabinet and the executive".

As the South African currency continues to lose value, higher borrowing costs also mean the government will have less money for investment projects aimed at stimulating the sluggish economy.

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Africa, South Africa, Politics