The council is considering privatising its waste collection service
Leeds City Council has attacked its bin service as "inefficient", as a strike by refuse workers enters its fourth week.
The authority said overall collection rates were 20% less efficient compared with the average council.
The council also said staff took 30 days sickness per year, a figure up to four times higher than it would expect.
Unions have reacted angrily, saying it was unfair to compare the collection rates of different councils.
Unison and the GMB also said the physically demanding nature of the work meant there was a higher sickness level among refuse collectors and street cleaners than in some other professions.
The strike centres on union claims that the council plans to cut refuse collectors' annual salaries by up to £5,000 from February 2011.
In a statement the council said: "Unfortunately Leeds has a very inefficient and costly refuse collection service."
Council leader Richard Brett added that the collection and sickness statistics were some of the reasons why the council was considering privatising the service.
"I do have sympathy with the strikers and their families and would urge them to come back to work so that we can continue negotiations about the potential for addressing the pay gap and modernising the service," he said.
"The current stalemate isn't any good for anyone."
Tony Pearson of Unison, said: "It's an absolute joke to talk about an industry average collection rate because there are different collection practices. Leeds workers, for example, pick up rubbish that other councils don't.
"And do the council seriously expect there won't be long term sickness in occupations where there is such physical wear and tear? It flies in the face of reason.
"It is as if they are trying to conduct some sort of propaganda war in order to privatise the service."