Bosses at South East Coast Ambulance Service are demanding workers accept a 25 percent pay cut, or the loss of 30 jobs.
Directors of the Trust, which is bidding for foundation status, want to reduce unsocial hours payments that staff receive for working around the clock.
Some workers could lose up to £5,000 a year.
GMB regional organiser Rob Macey said, “We will fight these proposals.”
Enough is Enough launches on 17 August
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United strikes are needed