Union leaders are demanding urgent talks with Staffordshire Police Authority after a long-running pay dispute failed to be resolved.
Authority members had thought the threat of legal claims for sex and age discrimination was over after last week authorising a pay rise for 280 of the force's 1,168 police staff.
It follows a decision to reduce the number of pay bands for police staff which will see workers in lower pay bands move up to higher scales, costing the force £390,000-per-year.
But authority members refused to back-date the pay rise to April 1 this year – a decision that will save £220,000.
Now Unison leaders are refusing to support the offer and warn the authority could be hit with a legal challenge.
The row centres on pay scales introduced in 1999 which unions claim mean it takes too long for workers to climb into the higher pay bands.
It also opens police forces up to sex discrimination claims because the current pay bands allow overlaps, meaning groups of women or men in lower bands could be receiving similar pay to staff in higher bands but with different terms and conditions.
Unison's Staffordshire branch secretary Michael Shepherd said: "Back-dated pay was always the agreement in principle. That would prevent us from taking legal action in the future on the grounds of age or sex discrimination.
"But we believe Staffordshire Police Authority has put itself in legal jeopardy by not back-dating the pay.
"It is likely a tribunal would find against them, whereas if they did back-date the pay, it sends out the message they do recognise the pay structure was wrong and an intent to put it right.
"I'm meeting with the police authority on Monday to say, 'please come back from the brink'. There's no need to save a few pounds when it would cost far more in litigation."
Unison has been in talks with the police authority for more than a year.
The dispute comes as the force needs to save £38 million by 2015. A pay freeze is also still in place.
Speaking to the human resources committee, Graham Liddiard, pictured, the authority's director of resources, said: "In 1999 the concerns of Unison and general best practice were on creating large grades to give career development opportunities in the same role.
"It's interesting how things change because we are now in a position where large pay bands cause problems with age and sex discrimination – taking 11 years to get to the top of the band.
"Some groups are disadvantaged and if a group was predominantly female, or male, that could also mean a significant risk of claims coming forward.
"Unison has rightly said it has waited too long for a decision already."
Police authority chairman David Pearsall said: "Unison has been patient with us. They could have been much more bloody-minded."
Authority member Leigh Gothard said: "Back-dating the pay to April would put us in an invidious position and set a precedent for the future."
Staffordshire Police Authority declined to comment on today's talks.
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