A union is launching legal action on behalf of more than 1,800 Monarch airline workers who lost their jobs after the firm went into administration.

Unite, which represents about 1,800 engineers and cabin crew who worked for Monarch, announced it will begin employment tribunal proceedings over an alleged failure by the company to consult on redundancies.

Meanwhile pilots’ union Balpa claimed some of its Monarch members were left with a phone bill of almost £40 after being asked to call a premium rate line to join a telephone conference in which their redundancies were announced.

Administrator KPMG agreed to reimburse the staff following pressure from the union.

Under UK law, companies with more than 100 employees must give at least 45 days’ notice of their intention to make people redundant.

Administrator KPMG made 1,858 workers redundant on Monday, hours after Monarch’s collapse was announced.

Unite national officer Oliver Richardson said: “Through no fault of their own, former Monarch workers are out of pocket and out of a job.

“The manner in which Monarch went into administration and the way the Government allowed it to 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.”

Balpa general secretary Brian Strutton described the treatment of pilots as “unbelievably cold hearted”.

He went on: “Since Monday we’ve seen appalling treatment of Monarch staff.

“Not only were they given no warning of this situation but some have had to shell out their own cash to be told they’ve lost their job.”

Jet2.com said it will increase flights at airports previously served by Monarch due to “increased demand”.

A Jet2 plane(Owen Humphreys/PA)

The airline is adding more than 100,000 seats on flights at Birmingham, Manchester and Leeds Bradford airports this winter.

Administrators are considering breaking up Monarch, which was founded in 1967, as no buyer was found to purchase it in its entirety.

The group’s engineering operation, Monarch Aircraft Engineering Limited, is not in administration and continues to trade normally.

More than 30% of the 110,000 passengers who were abroad when the airline went bust are expected to have returned to the UK by Wednesday night in the country’s biggest peacetime repatriation, which began on Monday.

The Civil Aviation Authority (CAA) arranged 119 flights to bring back more than 23,000 people in the first two days of the operation.

All remaining customers are expected to have returned by October 15.

The flights are costing the Government around £60 million.

Some 750,000 people who held future bookings for Monarch flights or holidays have had their plans disrupted.