Editor of Which? Travel Rory Boland said some holidaymakers were notified their easyJet flight had been cancelled on the day they were due to travel, which he described as "totally unacceptable".
"We continue to hear concerning examples of the airline failing to fulfil its legal obligations to passengers and ignoring their rights," he continued.
"If a flight is cancelled within 14 days of departure, passengers could be entitled to compensation and should be offered the option of being rerouted using another carrier if necessary.
"We know this requirement is not always being met, so the government and CAA must intervene where airlines are playing fast and loose with the rules."
Boland said the "cavalier approach" some airlines are taking towards their customers is a reminder of why passenger rights "must be strengthened".
"The government should drop plans to slash compensation for delayed and cancelled domestic flights and give the CAA direct fining powers so it can properly hold airlines to account when they flout the law," he added.