Some companies haven’t signed citywide contract; union says job security is top issue.

Hotel workers voted overwhelmingly Tuesday to authorize a strike at some of Boston’s biggest and most prestigious hotels if the companies don’t agree to a new citywide contract.

Fifteen of the city’s 24 unionized hotels have already signed the new five-year contract, which raises wages and benefits by 4 percent a year and strengthens protections for workers if a hotel is sold or goes into bankruptcy.

Here’s a typical union tactic: Complain about the members’ pay levels or working conditions, with a goal of engendering the public’s sympathy.

But Brian Lang, president of Unite Here Local 26, is taking a different approach with his union’s latest contract negotiations. Lang knows his members make a decent living wage. He just wants to keep it that way.

Local 26 represents more than 4,000 hotel workers among 27 hotels in the Boston area. Contracts for 24 of those hotels — those within Boston’s city limits — expired at the end of February. So far, Lang says the union has new five-year contracts lined up for workers at 14 of the 24 hotels. He says the contracts’ parameters —such as a 4-percent annual increase in pay — stay the same among all the participating hotels, even though only some are negotiating together as a group.