Other industrialised nations are either phasing out the method or reducing the amount of time sows are kept in the metal crates, which are so small the animal cannot turn around or take more than one step forward or back.

In 2017 Australian pig farmers will have to reduce the maximum amount of time they keep sows in stalls from 16 weeks - the entire pregnancy - to six weeks.

Under the new code - approved by federal, state and territory agriculture ministers on Friday - the length of the stalls will increase from two metres to 2.2 metres, and remain 60 centimetres wide.

The bioethicist Peter Singer says Australia risks being left behind in animal welfare standards as Britain, the US, Canada and the European Union either reduce the amount of time gestating sows spend in stalls or ban the practice altogether.

The Australian-born Princeton University professor said the $818 million Australian pork industry could no longer justify the use of stalls when the world's largest pork producer was replacing them with larger pens housing small groups of pigs.

Source: The Sydney Morning Herald