The decision was made at the FSA's board meeting on Wednesday (7 August), and the FSA will now write to Defra ministers to advise them not to go along with Brussels' proposals.
A spokesman for the FSA said a relaxation of the ban had been opposed because greater clarity was needed on how feed controls would be enforced.
The FSA's decision comes after its own research indicated most British consumers would be against relaxing the ban.
Last month, the FSA conducted consumer focus groups after Brussels proposed that the current outright ban on feeding animal protein to livestock be lifted for non-ruminants such as chicken and pigs.
The final decision on whether the UK will oppose a relaxation on the ban will be made by ministers.