Consumers could be prosecuted for reusing second-hand stamps as a vast online market is revealed.
A first class stamp now costs 67p, but uncancelled ones are available for as little as 16p on sites including eBay.
The Daily Telegraph discovered a booming second-hand market with eBay alone hosting more than 2,100 listings for re-used first and second class stamps.
One seller told the Telegraph they sell 20,000 reused stamps a month, claiming that they had had “no issues to this day” with the stamps they sold.
Another seller said used stamps are largely acquired by exploiting charities that sell on their received envelopes in large quantities as a way to supplement their incomes, usually to stamp collectors.