Spanish authorities have slapped fines on budget airlines Ryanair, easyJet , Vueling and Volotea totalling 150 million euros ($163 million), consumer groups who lead a six-year campaign against the charges said on Friday.

The fines are a challenge to budget airlines' business models, which hinge on charging rock-bottom fees for tickets and adding supplements for things like larger carry-on bags that were previously provided free by traditional airlines.

Spain's Consumer Rights Ministry fined the carriers for violating customer rights when charging for larger carry-on luggage, picking seats or boarding pass printouts, while not allowing cash payments at check-in desks or to buy items on-board, said consumer rights associations OCU and Facua which have been challenging the practices since 2018.

The ministry opened an investigation in 2023.

OCU said in a statement it expected other European countries to follow suit and also to punish those same "abusive practices."

Spanish airlines industry group ALA, which confirmed the fines, was quick to criticise the government decision as violating the European Union's single market rules and the companies' freedom to set their own prices.

"We defend the consumer's right to pick the best travel option," ALA President Javier Gandara said in a statement, adding that Spain's decision would force as many as 50 million passengers who only travel with a small bag under their seat to pay for services they do not require.

The Consumer Rights Ministry had no immediate comment. Ryanair, Volotea and Vueling declined to comment on the fine since ALA spoke on their behalf.

In 2019, a Spanish court ruled Ryanair's policy of charging a fee for hand luggage was "abusive". However, Ryanair continued with its policy, citing airlines' commercial freedom to determine the size of their cabin baggage.

The success of the budget airlines and the appeal of their low-ticket price policy has forced many legacy airlines to stop offering services such as free food and drinks or entertainment in short- and medium-haul flights.

($1 = 0.9242 euros)

(Reporting by Inti Landauro and Emma Pinedo; Editing by Andrei Khalip and David Holmes)