The consumer advice association said it had seen evidence of certain carriers “reneging on promises” made to the CAA to improve their refunds process amid the pandemic.

Following a report into airline refunds released on 30 July, the CAA said despite commitments from airlines to speed up the issuing of refunds it “will not hesitate to take further action against any airlines where necessary”.

Chief executive Richard Moriarty added: “There is still work to do. We have required commitments from airlines as they continue the job of paying customer refunds.

“Should any airline fall short of the commitments they have made, we will not hesitate to take any further action where required.”

However, Which? said it had since identified a number of airlines it believed were “falling short” of the promises they had made to the regulator, believing a lack of enforcement would “set a precedent that sees airlines continue to treat passengers unfairly without fear of consequence or sanctions”.

Which? is calling for the government to “enhance” CAA powers to make it easier for “swift and meaningful action” to be taken against airlines that are repeatedly highlighted to be breaking refund rules.

Editor of Which? Travel, Rory Boland, said: “Time after time, Which? has exposed airlines breaking the law on refunds for cancelled flights due to the pandemic and treating their passengers unfairly, and we’re concerned that they now feel empowered to do as they please without fear of punishment. 

“Passengers must be able to rely on a regulator that has effective powers to protect their rights – especially at a time of unprecedented turmoil.

“The government needs to step up and ensure the CAA has the tools it needs to hold airlines to account, or risk consumer trust in the travel industry being damaged beyond repair.”

In response, CAA spokesperson Andrew McConnell said: “We thank Which? for their continued engagement on this important matter. 

“We will review any supplementary evidence that Which wish to provide to us beyond the 12,000 cases previously submitted during our review of airline refund policies and performance during the Covid-19 pandemic.
 
“While our initial review has concluded, we have been clear that we will continue to monitor performance closely and should any airline fall short of the commitments they have made to us, we will take further action as required.”