Keith Temple, 75, bought the caravan at Haven Seashore holiday park, on North Denes in Great Yarmouth, 18 months ago for £60,000.

But when he decided to sell the mobile home back to the park earlier this year, due to health-related issues, he was offered £24,000.

"We thought that was disgusting," he said.

Haven Seashore Holiday Park, on North Denes in Great Yarmouth. (Image: Archant)

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Mr Temple, who worked in the James Paget Hospital for eight years and now lives in London with his partner Tony Warnock, said they did not accept the offer.

Haven then increased the amount to £34,800, which the couple "reluctantly" accepted, he said.

"That was my retirement money. I worked 50 years to give them [Haven] £30,000. It's an awful thing to go through.

"You work all your life for your pension money, then you lose half of it."

A spokesman for Haven said: “We offer all of our customers the option of owning their dream holiday home through a wide range of caravans to suit every taste and budget.

"Before any purchase is completed, we explain to all potential buyers that the resale value of the caravan may be subject to change and could reduce over time," they added.

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Mr Warnock, 66, said: "Nobody explains this when you're buying the caravan, how it is going to depreciate in value.

"When it comes to be resold, they treat it as though you are selling a car.

"I don't understand how anything can depreciate that much over 18 months."

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The couple said they are concerned other people could "fall into the same trap".

Mr Warnock added: "We want to find out where that money has gone. Has it been swallowed up in Haven's profits or redistributed among sales reps?"

Haven said they offer all existing owners the "more convenient option" of selling their caravans back to the park - but also encourage them to consider selling to a trader or privately.