With online porn revenue falling for all but the biggest adult groups, the tricks employed by marketeers are becoming dirtier.

A new scam sees staff for adult websites masquerading as lonely hearts on dating sites to con people into signing up for pay-per-view material.

They post apparently genuine personal ads on sites like Yahoo.com and popular dating site Match.com, designed to entice viewers to adult websites.

Prospective victims are contacted to arrange a real-world meeting but are first asked to view their 'date' via a webcam site, which requires handing over email details and maybe even paying an access fee.

At the very least, suitors open themselves up to floods of spam. And, according to MSNBC, many lonely hearts are falling for the trick.

A spokesman for Match.com said it was tough to screen out carefully crafted personals that appeared to be legitimate. The company's only real defence against the porn scam is customers' complaints, he added.

The spokesman said that rogue profiles are removed immediately after the company received a complaint. Those that have yet to generate any complaints are usually found and removed within a week or two of being posted, he added.

But adult websites have said that they too are suffering, and that the scam is the work of a handful of unofficial websites piggybacking on the brand name of better-known adult website networks.

One group, FreeNetPass, said the scam had cost its network members hundreds of thousands of pounds, as they have to refund money if people are conned into buying their product.

The company said rogue affiliates are responsible, and that the practice violated FreeNetPass's policies.