Around 900 members of the PCS and Prospect civil service workers’ unions working for the Maritime and Coastguard Agency (MCA) are balloting for strike action in a dispute over pay.
MCA pay levels are behind those paid to other emergency services and below inflation cost of living increases.
The workers have been taking part in industrial action short of a strike since May last year. In December, 90 percent of members voted in a consultative ballot to show their willingness to strike.
Coastguard watch assistants participate in search planning and other duties in response to 999 calls, but they only earn the national minimum wage.
PCS members in the MCA take on both administrative and operational duties for emergency and 999 distress calls, anti-pollution measures and ship registration.
They operate out of 19 rescue co-ordination centres. They also look after the River Thames and other inland waterways.
Prospect members are MCA surveyors. The strike ballot closes on 27 February.