When the agency launched an investigation into 32 online travel companies at the end of September, it found that 13 of them were breaking the law.
Golden Air and Gotlandsflyg were both found to offer illegal terms and conditions in their customer contracts. Both companies wrote that they under no circumstances would compensate passengers for delayed or cancelled flights.
In a further eleven cases, the agency found that travel companies had included hidden costs – such as insurance – in the total price. The firms in question were Seat 24, Travellink, Doodle, Travelpartner, Mr Jet, Supersaver Travel, Flygvaruhuset, Big Travel, Travelstart, Resfeber and Sky Tours.
In addition to the Swedish providers, Irish company Ryanair was also found to have hidden costs. The agency said it would seek to resolve the problem by enlisting the help of the Irish authorities.
The investigation carried out by the Swedish agency is part of a wider European study due for release on Wednesday afternoon.
“What we are going to do now is write to these companies and ask them to cease using this kind of marketing,” said Henrik Hoffmeister, a legal expert at the Swedish Consumer Agency.
“If they refuse we can threaten them with fines before passing the case on to the Consumer Ombudsman,” he added.
The ombudsman can then decide if it is necessary to take the companies to court.
Hoffmeister said the agency was somewhat surprised by its findings.
“We had maybe expected more to find that not all costs were included in the price. That is what we get most complaints about.”