Figures released today show across England and Wales 5,000 dogs, believed to be banned breeds, have been confiscated by police.
Pitbull terriers, Japanese Tosas and Argentine mastiffs are breeds banned under the 1991 Dangerous Dogs Act.
However, the RSPCA wants the Dangerous Dogs Act to be changed so dogs are banned on the basis of behaviour not breed.
Although the government accepts that any dog can become dangerous in the hands of irresponsible owners, ministers claim the ban on certain types of dog is crucial in helping to deal with the heightened risk those animals pose.
Since 1997, some dogs can be exempt from the ban if a court rules the animal is not a danger to the public, but the RSPCA said the assessment process is difficult because it is based on the dog's appearance rather than genetic heritage.
The animal welfare charity said there is no evidence to show breeds such as pitbull terriers are generally any more likely to show aggression than other types of dog and wants a change in the law.