Five years ago, only a handful took place. Experts suspect thousands more have fallen prey to the gangs without contacting the authorities about their plight.
Officers from the National Crime Agency (NCA) warned that Britain is being targeted by gangs in Morocco, the Philippines and the Ivory Coast.
They have discovered criminals running factory-style centres, with 'honey trap' actors, blackmailers and financial centres laundering payments.
Investigators said the gangs targeted individuals through Facebook, dating sites and even professional networking site LinkedIn. In most cases they appear to single out potential victims based on their 'ability to pay' and because 'they have something to lose'.
Ransom demands can vary from a few hundred pounds to several thousand, with the money sent by anonymous wire transfer.
Scottish prosecutors are trying to extradite a Filipino man over the death of 17-year-old Daniel Perry in July 2013. The teenager, from Dunfermline in Fife, killed himself after being lured into a webcam chat.
Last year, schoolboy Ronan Hughes, 17, from County Tyrone, Northern Ireland, also committed suicide after posting pictures of himself online.
Investigators said the blackmail was a 'deceptively simple crime', which involved criminals using fake identities to befriend victims online.
They then engage them in online conversations via video messaging software, which quickly turn sexual.
The goal is to persuade the victim to undertake a compromising act on webcam, which is secretly recorded and then used to blackmail them.
NCA figures showed that the highest proportion of victims are men aged between 21 and 30. The youngest person targeted was just 11.
The agency has released a YouTube film aimed at warning the most vulnerable potential victims of the danger they face.
Scotland Yard Assistant Commissioner Martin Hewitt, the national lead on adult sexual offences, said: 'This is a deeply worrying emerging threat.
"We have seen four young men take their own lives because they saw no other way out. It is a damaging and invidious crime."