The charity has accused the Government of "scapegoating" badgers for the increasing incidence of TB in cattle, and argues that there is overwhelming evidence to refute a link.
An eight-year study on the subject came to an end last year and public consultation is continuing until 10 March.
An RSPCA spokeswoman said: "The Government's own research shows that the situation actually got worse in areas where badgers were culled to see what effect it would have on cattle."
The charity ran newspaper adverts last week urging people to email, text or write to Defra to object to further badger killings.
A Defra spokesman said: "We will consider the views made by all who contribute to the process."