The redundancy package for Essex Police support staff has been reduced shortly before a series of job cuts are due to be made.
The police authority cut the payout so from 10 December staff will receive 1.3 times the statutory minimum-which is about a week for each year worked.
Previously the package was more than three times the statutory minimum.
The authority said due to Spending Review budget cuts it had to make redundancy affordable.
If a police support staff member earns £20,000 a year, under the previous redundancy scheme they would have been paid about £1,308 for each year they worked.
Under the new scheme they will receive £665 for each year worked.
The police authority said in a statement: "Bearing in mind that this is a four year programme and is on an unprecedented scale, it is vital redundancies are affordable in the long term."
A spokesman for Unison said early signs were 600 police staff posts would be at risk in the next four years.
Unison said they were against the move and were taking legal advice to see if they can challenge the decision.