President Jacob Zuma has lost the support of his biggest political ally,Congress of South African Trade Unions, COSATU.

The union which is South Africa’s biggest trade union called on President Jacob Zuma on Tuesday to quit after his cabinet reshuffle cost the country one of its investment-grade credit ratings and deepened splits within the ruling African National Congress (ANC).

Cosatu’s statement came moments after Zuma made his first public remarks about Thursday’s sacking of respected finance minister Pravin Gordhan, which rating agency Standard & Poor’s cited as a reason for its downgrade of South Africa to “junk”.

In remarks echoed by new finance minister Malusi Gigaba, Zuma said fiscal policies would not change and that people should remain calm after the rating cut.

He also urged his cabinet to reach out and reassure international investors following the dismissal of Gordhan, a totem of policymaking stability for many, whose departure has rocked the rand currency and other local assets.

But the union, allied to Zuma’s ANC, said it no longer believed in his ability to lead, and that it wanted to restructure its alliance with the party.

“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. We no longer believe in his leadership abilities,” Cosatu said in a statement.

Defending the reshuffle, Zuma said he expected the addition of “many young ministers” to “add renewed energy into Cabinet and the executive,” Zuma Said.