American pit bull terriers will have to be desexed under new laws to eradicate the dog breed from Victoria.

The State Government says no new pit bulls will be allowed to be registered after the laws take effect in the next few months.

About 600 pit bulls are registered in Victoria and the breed was responsible for about 50 attacks last year, although most of those were by unregistered dogs.

State Agriculture Minister Bob Cameron says pit bull owners will be able to keep their dogs if they are already registered.

"We want to do the right thing by those people. They can keep their pit bulls provided they are desexed," he said.

"However if anybody doesn't want to register their pit bull then that dog can be seized and destroyed by council enforcement officers."

RSPCA president Hugh Wirth has backed the new laws but says the Government needs to go further and ban the sale of pit bulls.

"The Government has been taking these things slowly," he said.

"This is a major step as far as the RSPCA is concerned, the next step will be a ban on trading."