Weekend reports said the operator’s managing director David Hopkins had written to clients warning them of the surcharge, stating: “It will be necessary and unavoidable for us, for the first time in many years, to invoke the surcharge contained within our contractual terms and conditions.”

One customer told the Mail on Sunday that she had learned last week her £869-a-head family January holiday in a chalet hotel in Meribel had been hit by the increase. However, she said she had found the same holiday being advertised on Mark Warner’s website advertised at £859pp to new customers.

Under the Package Travel Directive, certain circumstances – including currency fluctuations – can allow tour operators to add surcharges of up to 10% to holiday prices, without having to offer a refund,

A Mark Warner spokesperson said: “We have no further comment to make on surcharging other than to confirm that this is reflected in the cost of holidays on sale now, which are pitched to stimulate demand within the current market.”

Sunvil chairman Noel Josephides added: "If there are more surcharges - which is not a given - it is more likely to be ski companies than summer holiday companies. It is simply down to the rate of the pound at the time when operators publish their brochures."