Isle of Wight ferry operator Red Funnel insists it has contingency plans it can introduce if a proportion of staff walk out on strike this summer.
The Unite union has threatened to “shut down” all Southampton to Cowes ferry services in a dispute over pay.
About 120 customer service staff, shunters and ratings will be balloted for strike action between June 14 and July 5.
They have rejected a pay offer of 4.5%, rising to 6.3% for the lowest paid staff and are calling for an increase that reflects fast-rising cost of living which Unite says runs at 11.1%.
The Unite members represent about 20% of workers at the company, according to Red Funnel.
The ferry firm said it had contingency plans and would look to minimise disruption to services should industrial action be approved by the ballot.
Unite claims the majority of staff at Red Funnel are on the national minimum wage and are struggling with rising costs or rent and food.
The Red Jet fast passenger service makes a minimum of 21 crossings between Southampton and west Cowes on Mondays to Saturdays and 15 on Sundays. The car ferry makes at least 19 crossings daily between Southampton and east Cowes.
Unite regional officer Ian Woodland said: “A strike will cause severe travel disruption to and from the island. But the fault for that disruption will lay with Red Funnel, who need to recognise that many of their staff are sliding quickly into poverty.
“We urge the company to put forward a pay deal that reflects the soaring cost of living so strikes and the disruption they will cause can be avoided.”
General secretary Sharon Graham said: “These workers put themselves and their families at risk during the pandemic to keep the ferry services operating so food and essentials could reach the Isle of Wight. This is no way to repay them.
“Red Funnel must respect this workforce and pay fairly or face strike action.
“Unite is determined to win them pay that supports a decent living and, should our members take strike action, their union will be with them every step of the way.”
Red Funnel chief executive Free Collins said: “We are disappointed that our pay offer, which is positively aligned with our wider industry, has been rejected. We continue to engage in discussions with Unite regarding the pay claim for 2022 to secure a resolution and recognise our teams with a pay increase.
“Within seven days’ time, ballot papers will be issued to Unite members – representing 20% of Red Funnel colleagues. This ballot is to determine the members’ appetite for industrial action, which may or may not include strike action.
“The pandemic had an enormous impact on our revenues, and like many other businesses, we continue to face challenges particularly at a time when fuel costs are up 70%.”
She added: “We are very proud of the work our colleagues undertake daily in connecting the Solent, and we’re keen to recognise their commitment and dedication. We are pleased that pay claims for all other colleagues have already been settled for 2022.
“We must make sustainable decisions so that we can continue to provide lifeline services for our loyal customers, keeping the island connected and supplied. We are fully committed to doing all we can to ensure maximum travel choice and connectivity for island residents, visitors and businesses.”