They may have been constructed to be “indestructible” but increasing numbers of shopkeepers are refusing to accept new polymer bank notes because customers have taken on such claims as a challenge and are ruining them.

The new plastic money was hailed as the next chapter for bank notes after more than a century of cotton-based paper.

New polymer notes have now been issued this year by Royal Bank of Scotland, Clydesdale Bank, Bank of Scotland and the Bank of England.

But retailers say that that they are being bitten, ironed, put through tumble dryers and soaked in booze – and getting damaged in the process.

Newsagent Amit Patel said: “I’ve already refused to accept one after a customer presented it with what appeared to be damage caused by someone chewing one of the corners.

Another man told me he’d spent 10 minutes dipping a note in red wine to see if it would stain.”

Mr Patel, of Bexley, south-east London, added: “Customers see the ‘indestructible’ label as a challenge.”

When the new polymer notes were launched Bank of England Governor Mark Carney said they were “cleaner, stronger and safer” than the larger paper ones. They are said to last five years longer.

But Paul Baxter of the National Federation of Retail Newsagents said: “We’ve heard of people adding them to their wash, trying to tear them or letting their kids test them.”

Last week Stuart McLean, a print centre manager in Cambuslang, came forward to say that while he and colleagues were experimenting with the new Clydesdale fiver, he’d tried to erase a grubby mark on it with a simple old-school rubber – and ended up taking off all the printed images on the note.