Unite represents engineers and cabin crew who worked for Monarch and said it was lodging employment tribunal proceedings over a failure to consult on redundancies.
Oliver Richardson, Unite’s national officer, said: “Through no fault of their own, former Monarch workers are out of pocket and out of a job.
“While, understandably, a lot of the focus is on passengers, Unite is determined to ensure that Monarch workers, who worked so hard to try and turn the airline around, are not left high and dry.
“That is why Unite is doing everything it can to assist former Monarch workers in securing new jobs, offering free legal advice and launching legal action to secure the compensation they are owed, as well as helping members find jobs with other airlines.
“The manner in which Monarch went into administration and the way the government allowed it happen means there is a strong claim for compensation by former Monarch workers.
“We would urge former Monarch workers to lodge their details with Unite to help ensure they get the financial compensation they are legally entitled to.”