Federal member for Leichhardt Warren Entsch has thrown his support behind a cross-party group which wants medicinal cannabis use legalised.

A veteran federal Liberal MP wants marijuana legalised for medical use.

Far north Queensland Leichhardt MP Warren Entsch changed his mind about cannabis after seeing how it helped his late brother-in-law cope with the effects of an aggressive form of multiple sclerosis nine years ago.

“Towards the end of his life he started getting horrific shakes and the only way he could find relief was through using cannabis,” he said.

Mr Entsch has also been in contact with a Queensland mother whose 24-year-old son has cancer and uses cannabis to treat nausea caused by chemotherapy.

It’s also helped him gain weight and retain an element of hope, the MP said on Thursday.

“When you have a look at the profound improvement in the quality of life for people who are suffering from severe epilepsy or undergoing chemotherapy, you can’t argue against the benefits,” Mr Entsch said.

“We can’t deny them this reprieve from suffering when all else fails.

“As a parent I would do it in a heartbeat.”

Mr Entsch remains strongly opposed to decriminalising cannabis for recreational use but has joined a cross-party group which is preparing draft policy to legalising it for medicinal use.

Cannabis could be grown under license for the production of oil, which would have to be prescribed by a doctor.

Mr Entsch argues Australia already grows coca and poppies, both of which are used to treat pain.

“So why would it be any different for cannabis?”

“Policy makers have to be practical”