A Perth mother whose nine-year-old daughter suffers from chronic pain is calling on the WA government to take part in medicinal cannabis trials.

For chronic pain sufferers like nine-year-old Lily Poulter, life is about numbers.

For Lily the crucial number is five - that's the lowest amount of pain she feels every day on a scale of one to 10, 10 being the worst she's ever felt.

If it goes above five her mother, Nikki, has to increase the dose of her daughter's medications - Oxynorm, Tramadol and Lyrica - powerful painkillers with a list of side effects as long as your arm.

Ms Poulter knows her daughter's genetic connective tissue disorder, Ehlers-Danlos syndrome, which causes her joints to pop out, cannot be cured but wants to treat Lily's pain with medicinal cannabis.

She is calling on the Barnett Liberal government to take part in medicinal cannabis trials, which her doctors believe could be part of Lily's treatment.

"Just knowing the pain she goes through, it kills me", Ms Poulter said.

"Knowing fair well that there is a substance out there that can help her, which is natural, which isn't going to give her side effects.

"The worst part is the West Australian government is doing nothing to help us."

NSW, Queensland and Victoria have agreed to decriminalise cannabis for trials involving patients with epilepsy, end-of-life pain and chemotherapy-related nausea.

WA health minister Kim Hames has said the state would not join the trials because research needs to be done on a national scale.

Premier Colin Barnett has previously indicated he could support medicinal marijuana being given to patients in palliative care but maintained it was a very damaging drug.
Opposition leader Mark McGowan said the government was weak on the issue of medicinal cannabis.

"We should be leading the charge," Mr McGowan said.

"Let's face it, people like Lily aren't given access to this drug because her parents are law-abiding."