Budget airlines including easyJet and Ryanair have been hit with fines totalling €150m (£128m) by the Spanish government for policies that include charging passengers extra for cabin luggage.

In the biggest sanction issued by the Spanish government’s ministry of social rights and consumer affairs, the carriers easyJet, Ryanair, Vueling and Volotea have been penalised after an investigation launched last summer.

Under the judgment, the four airlines face being banned from charging passengers for cabin luggage in the future.

The Spanish news outlet Cadena SER reported that the fines would total €150m, with the airlines also being censured for charging passengers extra fees to reserve adjacent seats for children and other dependents.

The Spanish Airline Association (ALA), which represents the airlines, has hit back at the decision, calling the fines “disproportionate”, and pointing out that airlines could still appeal.

Ministry sources told the Guardian that the general directorate of consumer affairs had opened up an investigation in June last year after complaints by consumer organisations over “abusive practices” being deployed by the airlines.

The investigation focused on four areas, which included charging extra for cabin luggage and seat selection.

The government investigation also looked at concerns around a lack of transparency by the airlines over the final price of services when booking online, and the decision to block cash payments at the airport for additional services.

The sources said that the final sanction proposals had been put forward to the affected companies weeks ago. The ministry would not confirm the financial amounts each company has been asked to pay.

Cadena SER also reported that Ryanair had been censured by the ministry for charging passengers €20 to print off their paper tickets, calling this a disproportionate cost.

Facua, one of the consumer groups that filed the initial complaint, welcomed the decision, saying that it had been campaigning for six years to get the government to intervene.

ALA, which represents airlines carrying 85% of air traffic to and from Spain, said in a statement that the process was still open and an appeal could be lodged.

It also stressed that the practice was completely legal and that European legislation recognised the freedom of airlines to set their fares.

It said: “Sanctioning this practice limits the option to pay only for essential services and would force all passengers to contract the cabin baggage transport service, even if they do not need it.

“The consumer will be the main victim of this interference by the ministry of social rights, consumer affairs and Agenda 2030 in the European single market and the freedom of tariffs protected by European law.”

Ryanair, Vueling and easyJet referred the Guardian to the ALA for a response. Volotea has been contacted for comment.