The rising cost of postage is fuelling a market in reused stamps, allowing shoppers to buy them online for a quarter of the price.

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.

One worker at a Royal Mail sorting office claimed she sees 100 reused stamps make it through the system everyday as cost-cutting measures have led management to tell staff to turn a blind eye and no longer strike-out stamps by hand or issue penalty notices.