Dogs are being treated for stab wounds because youths are using them as weapons, the RSPCA has said.
The animals are also being treated for injuries such as cigarette burns and broken bones amid an increase in reports of street fighting.
Two-thirds of reports of dogs fighting are linked to young people using them as weapons, the charity says.
Scotland Yard said 719 dangerous dogs were seized in London last year, compared with 43 between 2002 and 2006.
The RSPCA said London was a hotspot for dog fighting.
The charity also identified West Yorkshire, the West Midlands and Merseyside as areas where young people "use dogs to fight and intimidate".
It said incidents of dog fighting had increased more than 10-fold from 2004 - rising from 24 reports to 284 in 2008.
David Grant, of the RSPCA's Harmsworth Animal Hospital in north London, said: "My staff are treating more dogs than ever for fight wounds and injuries sustained as a result of them being kept as status symbols by young people who think having a dog makes them look tough.
"I've had to treat dogs with stab wounds, broken bones and even cigarette burns to their heads. The torture some of these poor animals have suffered is simply horrific."
Almost 300 seized dogs are being kept in kennels awaiting court proceedings at a cost to the taxpayer of more than £1m a year.
Mr Grant said breeders charge up to £500 for puppies which are then sold to young people with little experience of caring for them.
He said many dogs are soon abandoned by their owners, adding to the large numbers of bull terrier breeds, Rottweilers and mastiffs in animal homes.
Mr Grant said: "These latest figures only prove what the RSPCA's inspectors and animal hospitals have suspected for a long time, that more and more people are using dogs as a means of intimidation."
Supt Julia Pendry said Scotland Yard was "very concerned" about the increase in dog fighting and the use of dogs in anti-social behaviour.
"All dogs, especially certain breeds, need to be properly managed so they do not become aggressive," she said. "Owners have a responsibility to keep their dogs under control."
The maximum penalty for allowing a dog to be dangerously out of control is two year's imprisonment, a fine or both.
The Met has launched a Status Dogs Unit to work with the RSPCA and councils to encourage responsible dog ownership.