A DECISION by the South African Local Government Association (Salga), the government employer, to start talks over municipal workers' benefits with a clean slate will delay already struggling labour negotiations, unions have said.

The Independent Municipal and Allied Trade Union (Imatu), which represents municipal workers, on Monday said it was seeking legal advice to stop Salga from setting aside negotiated agreements.

The South African Municipal Workers' Union (Samwu), which has made joint pay demands with Imatu, said the prospect of a third municipal strike in as many years was becoming more likely because Salga was purposefully derailing talks.

The unions and employer are far from agreeing on wage increases, and a legal debate over workers' benefits is unlikely to cool relations.

Salga is offering a 4,5% general wage increase, which it raised from 4% earlier this month, but Samwu and Imatu want 13%, revised down from 15%.

Imatu said it was disappointed by Salga's notification to terminate the "main collective agreement and disciplinary code collective agreement" from July 1 this year.

Johan Koen, general secretary of Imatu, said his union had received a notice on May 23, adding he was unhappy with how Salga operated unilaterally, which weakened the bargaining process.

According to the notice, Mr Koen said, the collective agreements in question would expire by July this year and that Salga had the right, purportedly in terms of section 23 (4) of the Labour Relations Act, to terminate the agreements by giving notice.

"The current collective agreements protect our members' organisational rights and conditions of service such as working hours, overtime rates, maternity leave and sick leave," he said.

Mr Koen added: "Salga effectively wishes to ignore all the time, money and resources that went into the establishment of the collective agreements and start again. Imatu cannot accept a blatant move to diminish the existing rights of our members."

Salga said it would comment but failed to do so on Monday.

Municipal workers last went on strike in August 2011 for two weeks, demanding an 18% increase but ultimately agreeing to the state's offer of 6,08% through Salga.

Tahir Sema, spokesman for Samwu, on Monday said members of his union were prepared to strike again if Salga did not budge on its below-inflation pay-hike offer.

"Talks are not going well, but we are confident that we can achieve a double-digit increase, " he said, adding: "The move by Imatu for legal action shows that Salga is undermining the negotiations."

About 160000 out of 200000 workers who negotiate through Salga's bargaining council are Samwu members. The remainder are Imatu members.

John Brand, labour negotiations expert at Bowman Gilfillan Attorneys, said strikes took more from workers than they gained from them.

"If one examines most of the big strikes last year, then one sees that in some cases workers gained nothing out of the strike, in that they returned to work on the basis of the employer's last offer," he said. "The worst example was the municipal strike. In most of the others they gained slightly from the strike, but that was heavily outweighed by loss of earnings during the strike, which it will take many months and in some cases years to recover."