An ad for a Walkers crisps competition which offered 20,000 holidays has been banned after more than 100 complaints to the Advertising Standards Authority (ASA) that the trips were virtually impossible to win.

The 'Spell and Go' competition encouraged customers to collect codes on crisp packets. Once a code was entered online, customers were given a letter and could then collect more letters to spell out 26 possible destinations, with those who completed the name of a location winning a holiday.

But customers took to social media to complain that it seemed impossible to get letters C, D or K to complete the names of some places. In total 112 people complained to the advertising watchdog about the competition, which had been advertised on TV and social media since May.

Walkers defended the competition, saying all 26 destinations included at least one of the letters C, D or K – known as 'type 1' letters – and that there were enough of these letters in circulation for 20,000 holidays to be won.

Out of the 20,000 holidays up for grabs, just 796 people ended up being lucky enough to win one. New York, Hong Kong and Tokyo were just some of the possible destinations.

'Likely to cause disappointment'

After investigating, the ASA said it was satisfied there had been enough type 1 letters, but found that another part of the competition had breached its code – the 'random swap' function on the Walkers website. This allowed participants to swap letters they didn't need for another letter.

The ASA found that despite the Walkers website stating that "all letters are treated equally", the 'random swap' pool was actually only made up of type 2 letters, meaning C, D or K could not be won.

The ASA said it "considered the original limitation of the random swaps mechanism to only type 2 letters was a significant condition likely to influence a consumer's decision" and the omission was "misleading and likely to cause unnecessary disappointment to consumers".

It told Walkers that in similar future promotions, it must ensure "significant conditions for all aspects of the promotion were communicated to consumers".

A Walkers spokesperson says: "We appreciate that the online letter swapping mechanic could have been clearer and we will ensure all future promotions take this feedback on board".

They add: "Our Spell and Go promotion has been very popular and we've given 796 families four-star, seven-night holidays worth over £1.35 million.

"We're aware some customers are disappointed that they haven't been successful in winning a holiday. Twenty-thousand holidays could have been won if all the promotional packs in the market had been played and we would have honoured all of those should that have been the case."

'I spent over £50 on Walkers''s Coupon Kid Jordon Cox was among those scrabbling to find packs of crisps with the right letters.

He says: "The whole thing was a massive shambles! Being an avid comper, I was one of the first people to grab some Spell and Go packs when they first came out in May. Immediately it became apparent that the elusive letters would be 'C', 'D' and 'K' – every destination had at least one of those letters in.

"What was so enticing reading into the T&Cs was that even if you spelt out a city that you didn't want to go to, you could've exchanged it for £2,000 or £4,000 in holiday vouchers depending on the location.

"I collected over 100 packs of crisps during the promotion and spent over £50 on Walkers… but once I collected every letter other than 'C', 'D' and 'K', I kept getting duplicates. Nearly every other comper I came in contact with had the same issue."

For full help on making the most of competitions, including how to use web gadgets to form-fill at speed and where to find free help with tie-breakers, see our 44 Comping Tips guide.

Additional reporting by the Press Association.