Ofcom has joined forces with similar communications regulators from the US and Canada in order to tackle the problem of number spoofing.

Number spoofing is where unsolicited, misleading or, at times, fraudulent telemarketing callers use fake or stolen number IDs to make you think they are calling from a firm you might recognised. The spoofed number might be a random series of digits or the telephone number of a real company.

Not only can this cause you to pick up if you recognise the number or think it looks genuine, but it also prevents you from calling them back or to opt out of future direct marketing calls from that organisation. It also makes it difficult for regulators to trace companies making nuisance calls.

Spoofed number calls are being originated from all over the world and, says Ofcom, account for a significant and growing proportion of nuisance calls. That is why it has joined the international taskforce in order to pool resources and share intelligence.

"International co-operation is vital in finding effective remedies to the problem of number spoofing. We are thoroughly committed to this joint effort and are determined to put a stop to this harmful practice and take action against those responsible," said Claudio Pollack, consumer group director of Ofcom.

Ofcom also publishes a guide for UK consumers on preventing and complaining about nuisance calls, which is available on ofcom.org.uk