The Morrison government is expected to release draft legislation next month which would allow "three-parent IVF" to treat mitochondrial disease.

Some religious politicians have previously opposed laws that allow genetic modifications.

Opposition Leader Anthony Albanese backed giving caucus members a conscience vote at a meeting in Canberra on Tuesday.

"No one should ever have to choose between their genuinely held commitment to their faith and their support for our party," he told colleagues.

Both major parties will be allowed free votes after the coalition agreed to the same position earlier in the month.

The rare disease passes on DNA mutations to babies, but mitochondrial donation can provide a way for children to be born unaffected.

The most serious symptoms affect one in 5000 babies, with the disease potentially causing strokes, hearing and sight loss, and the inability to walk, eat, swallow or talk.

It can also lead to liver disease, diabetes, heart, respiratory and digestive problems and intellectual disabilities.

Labor MP Mike Freelander, who is a doctor, told the caucus meeting he had treated children with the disease which had a horrible impact.

The treatment involves replacing mitochondrial DNA from the mother with healthy mitochondrial DNA from the egg of a woman who is a donor.

Draft legislation is expected to be released in March before a likely vote in May or June.

The donations may be the only chance for some parents to have a genetically related child without mitochondrial disease.

In 2018, a Senate committee recommended the technique also known as "three-parent IVF" which is legal in the UK.

The report noted the strong potential of partial genetic donation to address the debilitating effects of inheriting mitochondrial disease.

Australian Associated Press