The workers were paid two hours salary by their employer, Glad Group, to protest outside the NSW head office of United Voice in Haymarket.

The striking workers held placards which said "I am glad I have job security", "United Voice is not my voice, you don't speak for me", "United Voice = Disunity" and "My Voice is heard without United Voice".

Representatives of United Voice who watched on said it was the first time that workers had turned the tables on the union that represents them, by staging their own protest.

Rally organiser Paul Davidson, who is a supervising manager of the Glad Group employer, said the workers had presented a "united voice against United Voice".

He said the picket was "sanctioned and blessed" by the company who paid the striking workers for two hours to cover time taken for the industrial action. He said the cleaners were frustrated with union "meddling" in salary negotiations.

He said United Voice had stalled salary negotiations. Workers in the CBD received a three per cent pay increase from the company at one central Sydney site in George St this week. But workers outside the city have not received the same increase.

"While I'm sure United Voice wants to do the right thing, somehow this purpose has gone amiss and their interference is preventing us from receiving a much needed pay increase," Mr Davidson said.

"We're hoping that this show of unity will make it clear to United Voice that we want to get our increase, and for them to back down from whatever their motive is."

Mark Boyd, NSW branch secretary for United Voice, said the union had been trying to negotiate a renewal of the so-called Clean Start industrial agreement, which covers salaries and conditions.

He said Glad Group had shut down negotiations which have been ongoing since 2012, when the previous agreement expired. The union is asking for a four per cent salary increase as part of a new agreement that included existing conditions.

"Our organisers have spoken to the cleaners who don't really understand why they are here," he said. "If you work for a company and it says it wants you to do this and will pay you two hours to do it, the cleaners will do it because they are worried about their job security."

Mr Boyd said while the union did not oppose Glad Group's decision to award workers at one site a three per cent salary increase, it was trying to achieve a collective agreement for all workers, many of whom are foreign workers and students.

One of the protestors, Tonoy Ghosh, who works as a cleaner at Westfield in Sydney, said he had received a three per cent pay rise from the company. He said he wanted the company to "pay us by the rules".

"At the end of the day, I want the company to survive," he said. "The union is demotivating the workers".