Spokesman Christopher Zinn said yesterday, ''Well over half the hens described as free-range are housed in huge sheds, may never go outside, and their eggs may come off conveyor belts.''

A Choice investigation found there was no legal description of what a free-range egg should be, and that big producers had redefined the term to suit themselves.

The investigation also tested eggs for quality, and found 36 per cent of free-range eggs failed tests for freshness.

Choice recommended eggs be stamped with the date they were packed instead of unreliable best-before dates.

''While they might come out of the chook in great shape, they need to be refrigerated constantly for use-by dates to be valid,'' Mr Zinn said.

The investigation also found guidelines varied greatly between organisations, even though the eggs might all be branded ''free-range''.

The Australian Egg Corporation's quality assurance scheme, ''Egg Corp. Assured'', allows up to 14 birds per square metre inside a barn.

According to Choice, by comparison cage egg systems allow the space equivalent of 18 birds per square metre.

Other organisations only allow up to seven birds per square metre, including the RSPCA and the Free Range Egg and Poultry Association of Australia.

All of the current guidelines for free-range production are adhered to voluntarily.

Mr Zinn said if there was consumer pressure then ''something would get done about it, but people aren't aware of this issue so there isn't the pressure''.

Australian Egg Corporation communications manager Jacqueline Baptista said the 14 birds per square metre figure had been reached through scientific research and consultation with producers.

''We are absolutely dedicated to the welfare of the birds.''

Two of Australia's largest egg producers, Pace Farm and Aussie Pride eggs, both comply with ''Egg Corp. Assured'' standards. Family Homestead eggs were the only free-range eggs Choice found which complied with Free Range Egg and Poultry Association of Australia standards.

Ms Baptista said the Australian Egg Corporation was dedicated to the establishment of a national system to outline what free-range meant.

The RSPCA and Choice are also calling for uniformity.

Scientific officer for farm animals with RSPCA Australia Melina Tensen said consumers needed to understand what they were buying.

''Just because the carton says free range and has pictures of happy looking chickens adorning the cover doesn't mean the eggs have been produced to high welfare standards.''