The legality of many broiler breeds is being challenged in court this week in a case brought by the Humane League UK against Defra.
The animal welfare organisation has brought the judicial review, which is being heard in the High Court this week, to challenge whether 90% of the chickens reared in the UK are grown too fast to ensure their welfare.
The RSPCA will be giving evidence to support the case, it said, arguing in favour of slower growing breeds and lower stocking densities.
Kate Parkes of the RSPCA said: “We are pleased that we’ve been granted permission to act as an intervener in this ground-breaking case as our research clearly shows the welfare issues associated with these breeds is unacceptable.”