ABC reports that the supermarket chain's free-range standard allows for one square metre per hen, or 10,000 hens per hectare. And it allows densities of up to 12 hens per square metre inside sheds, as long as each hen is within nine metres of an exit.

But the RSPCA's farm animal scientific officer, Melina Tensen, says that's a more appropriate standard for barn-laid eggs than free range, and that there's no evidence that hens actually take advantage of the exits to move around outside.

The RSPCA says it wants evidence that hens aren't harmed in production systems that Coles would accept as 'free-range'.