In a media release, Saftu said South Africa's sovereign credit rating being downgraded to junk status by S&P Global "turned what was already a major national crisis into a potential catastrophe".
While the union federation said it condemned ratings agencies acting as "policemen for international monopoly capitalism", the S&P decision was facilitated by Zuma's reckless axing of ministers, giving S&P "a perfect excuse to act".
"We are another big step nearer to a descent into a failed kleptocratic state. It is now more vital then ever to mobilize the biggest ever protest movement to rescue millions of South Africans from the increased unemployment and poverty which will inevitably follow this downgrade."
Saftu said it has taken legal advice and decided to approach the high court to argue the President's actions were irrational and not in compliance with the Constitution and his oath of office.
"The main reason for filing a court challenge is that Zuma has once acted against the interests of the country in direct contradiction with his oath in which he swears to act in the best interest of the country," the statement said.
"The evidence will include statements by ANC leaders themselves, and now the ANC Integrity Commission, which has condemned the lack of consultation within the ANC and the use of a blatantly bogus ‘intelligence report’ to justify his actions."
The union movement, launched last month with former ANC-affiliated Cosatu general secretary Zwelenzima Vavi as its convener, would also continue its mobilisation of civil society, communities, religious groups and other workers’ organizations, and possibly set up a national crisis committee to co-ordinate ongoing campaigns against Zuma's presidency.
If Saftu has its way, a general strike is also on the cards, as the federation believes that winning on the streets is more effective than doing so at the negotiating table.
"SAFTU has therefore resolved to make a submission under Section 77 of the Labour Relations Act for a protected general strike on socio-economic issues. It will be based on the devastating effect the Cabinet reshuffle and the down-grading to junk status will have on workers’ jobs and living standards."