Forged banknotes increased 53% in 2005 on the previous year, according to the Bank of England. The number of notes detected was 505,000.

The jump was blamed on increasingly sophisticated criminal gangs using digital technology, such as top-of-the-range scanners, to produce notes of high quality.

The Bank also discovered that three gangs were responsible for most of the forgeries.

“The vast majority of forgeries are £20 notes,” explained a spokesperson for the Bank. “We are concerned at this increase and would urge the public to be vigilant when accepting these notes.”