The amount was revealed in accounts for the CAA’s Air Travel Trust Fund, which pays out in the event of the collapse of an Atol-holder.

The one-off sum is thought to include contingency planning for the collapse of Monarch Airlines, which was averted last September, although the CAA will not detail how much of the total this makes up.

The CAA chartered a fleet of aircraft, mainly from the US, and stationed them around Europe for around a fortnight while Monarch sought refinancing.

In response to the news, Abta said: “We understand from reviewing the Air Travel Trust’s published accounts that during their last financial year £25.6 million was spent on contingency planning.

“Given the scale of this cost, particularly in relation to the size of the overall ATTF, Abta will be writing to the CAA on behalf of Atol-licensed members.

“We will ask for clarification about the nature of these costs, whether the CAA anticipates similar costs being incurred in the future and, if so, how the ATTF will be protected against such costs.”

The CAA had justified the spending by saying it ensured it “was sufficiently prepared to manage a potential Atol-holder failure”.

Monarch was given a clean bill of health last October after owners Greybull Capital injected £165 million. The airline is back in profit and credit card companies, which had demanded it sell flight-only sales under Atol protection, no longer make this stipulation.