Number of fake £1 coins in circulation doubles to 30 million in just five years

Only then do you realise that it's a worthless fake.

Up to one in 50 pound coins in circulation is counterfeit, the Royal Mint said yesterday.

Fake pound: One in every 50 are forgeries

The number of fakes has doubled over the last five years and there are now more than 30million in use.

Currency experts believe criminal gangs are mass-producing the coins using specialised machinery.

Random sampling tests carried out by the Royal Mint found that 2 per cent of pound coins in use are counterfeit. The last time forgery figures were released by the Mint in 2003 the figure was 1 per cent.

Although fake coins can be distinguished by a few tell-tale signs, most go unnoticed.

Experts have warned, however, that when there are large numbers of counterfeit coins in use, businesses can lose faith and start refusing to accept even genuine coins.

Robert Matthews, who formerly tested coins as the Queen's Assay Master, said: 'In 2004, people stopped taking South African five rand coins because of concerns about the number of counterfeits.

Eventually, the coin had to be redesigned and recirculated. Surveys showed the number of counterfeits to be 2 per cent - the same as we've got here - and I'm worried that if we're not careful the same thing will happen to the pound coin.'

Mr Matthews said the number of fakes in other currencies is far lower. Only 0.1 per cent of euros - some 10million - are fakes, according to research in 2006.

He added that he was concerned that neither the banks, the Treasury, the Royal Mint nor the police were dealing with the problem.

But the Royal Mint insisted that the number of fake pound coins is low considering the numbers in use. There are thought to be more than 1.45billion in circulation.

It said: 'We track the counterfeit rate through regular surveys. The survey consists of taking a random sample of coins from across the country, and subjecting them to individual analytical inspection.

'It is a criminal offence to make or use counterfeited coins.' Anyone who suspected they had one should hand it to the police.

The pound coin, made from a mixture of copper, zinc and nickel, was introduced in April 1983 to replace the £1 note.

Since then, there have been numerous attempts to produce forgeries. Last year, a London man was jailed for making 14million pound coins for accomplices who paid him £2,000 in cash each week.