The figure was revealed as the Air Travel Trust (ATT) disclosed documents showing it repatriated 16,500 holidaymakers at a cost of £14.7 million in the last financial year.

A total of 19 companies failed during the period, the largest of which was All Leisure Holidays Group. This is almost double the 10 companies that failed in the previous year.

The CAA declined to name which Atol holder had prompted the £25.6 million spend, but in a statement, an ATT spokesperson confirmed the sum was for “contingency planning work and capability-building activities”. Accounts show the CAA spent nothing on this the previous year.

The statement added: “This planning ensured the CAA was sufficiently prepared to manage a potential Atol-holder failure, which required supporting large numbers of consumers, including a significant repatriation programme.

“Any large-scale failure would involve securing multiple aircraft and providing extensive customer communications across a number of channels,” it said.

It follows rumours last autumn that a fleet of US-owned aircraft including United Airlines’ Boeing 747s had been stationed around Europe and placed on Monarch Airlines’ schedules after the Monarch Group suffered a period of uncertainty which lasted around a fortnight in October 2016 until a cash injection was agreed.

There were also claims that other airlines were poised to operate flights from some of Monarch’s destinations such as Palma.

The airline was given a clean bill of health on October 12 after majority owners Greybull Capital pumped in £165 million. The cash means the airline’s scheduled sales no longer need to be covered by the Atol scheme.