The consumer champion surveyed nearly 2,000 holidaymakers about their experiences of all-inclusive holidays over the last two years, asking them to rate their provider on seven categories including customer service, accommodation, accuracy of descriptions and what was included.

Which? found respondents paid an average extra £258 a week inside and outside the resort.

The report said: “Shockingly, more than one in 10 people (13%) across the survey reported having to pay extra for local soft drinks on their ‘all-inclusive’ break as they were not included in their package, while almost a fifth of people (18%) reported having to pay extra for snacks.”

While 79% of respondents reported local alcoholic drinks included, only 43% had branded and premium alcohol as part of the package. Two-thirds of holidaymakers reported cocktails included in their package, and half had wine at no extra cost.  

Jet2holidays topped the list of 19 brands surveyed, with 86% of respondents reporting local alcoholic drinks included, and 78% finding snacks available at no extra cost. Kuoni was a close second and Saga third.

By contrast, Expedia clients spent the most on extras, with an average of £165 per week in the property and £228 outside. Only 44% of Expedia customers reported local alcoholic drinks included, dropping to a quarter for branded alcohol. Three in ten reported having to pay extra for local soft drinks. 

The worst performing company overall was Lastminute.com. Just 39% reported local alcoholic drinks included, and less than a third could access branded alcohol at no extra cost. Lastminute customers spent an average of £128 in the resort, and a further £238 outside.

Rory Boland, Which? Travel editor, said: “When budgets are tight, all-inclusive holidays surge in popularity, seemingly offering people a straightforward way to keep holiday costs under control with food, accommodation and drinks all wrapped into the price.

“However, our latest research has found that some all-inclusive holidays are far from being ‘all in’, with some unfortunate guests finding that even basic items like soft drinks weren’t included.”

Jet2.com and Jet2holidays chief executive Steve Heapy said the findings "should act as a true guide for customers and independent agents", adding the airline and operator’s status as a seven-time Which? Recommended Provider was a reflection of "hard work" the business puts into its customer service.