By Mike Dunn

PHILADELPHIA (CBS) – The largest of Philadelphia’s four city worker unions is turning up the heat on Mayor in long-stalled contract negotiations. They’re running anti-Nutter ads, including one to air during Saturday’s TV broadcast of the Phillies spring training game.

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“…but he still refuses to settle a fair contract with our union…”

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That’s from a radio-TV campaign paid for by District Council 33, the blue collar city workers union. Both DC 33 and the white collar union DC 47 have been without a new contract since 2009, and there’s been little evidence of progress in the talks.

“We want the public to know, we’re being treated unfairly. This is overkill with the mayor. The mayor wants to out-Rendell,” said DC 33 chief Pete Matthews.

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Mayor Nutter’s spokesman, Mark McDonald, said the mayor disputes the claims in the ads that the union has saved the city hundreds of millions of dollars. And he says negotiations between the two sides have been continuing on a regular basis.