The RMT union has warned ferry operators P&O that they are "sleepwalking into an industrial action ballot".
Last month P&O announced that it plans to axe 1,200 jobs and slash services to save money, blaming competition from low-cost airlines.
Job cuts are likely to be in Portsmouth and Dover.
The RMT claims there was a lack of consultation before the cuts were announced and has accused the company of "suffering from serious short sightedness".
RMT general secretary, Bob Crow, said: "P&O is trying to turn the screws with hints of selling off its ferry operations, but it will succeed only in infuriating RMT members already angered at the scale of the company’s proposed cuts."