The SA Democratic Teachers' Union (Sadtu) on Friday became the latest union to reject government's revised wage offer, saying it was ridiculous and an insult to workers.

"We call on the employer not to insult public service workers with such a ridiculous offer of a mere R10, from R620 to R630 for housing allowance and an unacceptable 6.5 percent for salary increase," said Sadtu general secretary Mugwena Maluleke in a statement.

Public service and administration minister Richard Baloyi said earlier on Friday that the employer would not budge from its offer.

The R630 housing allowance per month, was up from R500 and effective from 1 July.

Public servants wanted an 8.6 percent salary increase and a housing subsidy of R1000 with effect from 1 April.

Government previously made an offer of an increase of R620 but amended it with an additional R10 on Thursday.

Maluleke said Sadtu was continuing to mobilise members for a "total shutdown" on 10 August when the eight Congress of SA Trade Unions public sector unions (Cosatu) would march in Pretoria and Cape Town.

"Sadtu will embark on non-cooperation with the employer at all levels from August 6," he said.

"All members of the union will not attend any meetings, workshops or training convened by the employer at workplaces from that day."

National Union of Public Service and Allied Workers (NUPSAW) called on its members to start picketing during lunch breaks from Monday ahead of the strike action expected later in the week.

"NUPSAW firmly rejects government's offer. The union has exhausted and complied with all the negotiations processes to reach an amicable agreement, but again the employer shows no interest in addressing the union's demands."

The Independent Labour Caucus (ILC) and the Federation of Unions of South Africa (Fedusa) echoed Sadtu's sentiments that the revised offer was an insult.

"The improvement of R10 per month [for housing] is truly ludicrous and cannot be regarded as anything but an insult," the ILC which represented 11 public service unions said.

"It is virtually impossible to believe that the state is serious and acts in good faith by publicly stating that it wishes to avert a strike and then offers R10."

Fedusa's deputy-general secretary Gretchen Humphries said: "We also are of the opinion that the offer made by the employer is truly an insult thus provoking the ILC members to go on an industrial strike."

She said the R10 improvement to the housing allowance is "ridiculous and makes a mockery of collective bargaining and cannot be taken seriously".