The Public Servants Association (PSA) said it was concerned about government plans to cut the civil service wage bill in a bid to reduce South Africa's budget deficit and shore up the struggling economy.

The Federation of Unions of South Africa (Fedusa) also slammed the proposal, declaring war on finance minister Tito Mboweni and demanding that the matter be taken immediately to the Public Sector Coordinating Bargaining Council (PSCBC).

Presenting the 2020 budget to Parliament on Wednesday, Mboweni said the government would decrease its wage bill by about R160-billion over the medium term as part of efforts to lower spending and narrow a budget deficit projected at 6.8 percent of gross domestic product for the 2020/21 financial year.

In a statement late on Wednesday, the PSA said it failed to understand what it called the "continued attack on public servants’ salaries as a key focus to save the South African economy".

"The PSA cautions the minister and government that efforts aimed at minimising state expenditure should not come at the expense of those public servants who render services under enormous challenges," it said.

"The morale of public servants is dented and any unilateral actions by government in this regard are guaranteed to have dire consequences."

Fedusa, one of South Africa's three labour federations, came out guns blazing, saying the cut in the public sector wage bill rubbed salt into the wounds caused by another announcement on Tuesday that the government would no longer honour wage adjustments promised to public servants on April 1 as part of a three-year deal, because they were not affordable. 

"The issue of the public sector wage bill cannot be unilaterally decided by the minister of finance alone on budget day ... and should instead be taken to the PSCBC for proper discussions with public sector trade unions where it rightfully belongs," the federation said.

Fedusa said it was also disappointed that instead of announcing clear time lines for the restructuring of troubled State owned enterprises, Mboweni had instead "administered more of the same medicine of pumping more money into the resources guzzling monsters with an increased allocation of R111-billion".

It grudgingly applauded the decision not to increase taxes as many had feared prior to Mboweni's budget speech.

The National Union of Public Service and Allied Workers (Nupsaw) expressed disgust at the looming salary cuts, saying workers were taking the fall for corruption and mismanagement by the African National Congress (ANC) government.

"The government needs to act on footing (kicking) out those politicians who are looting ... stealing and interfering in department systems (rather) than reducing the wage bill," it said, accusing Mboweni of declaring war on unions.

"Nupsaw is ready to fight for the public servants and putting the workers first."

The Congress of South African Trade Unions, a key ally of the ANC, has already branded the budget as provocative, saying it found what it called the government’s continuous attacks on public servants "silly and tiresome".

"Workers will not play victims and the government can rest assured that they will demand and not beg for what is due to them. Cosatu remains battle-ready to pushback against this public service cuts agenda," it said.