Medical marijuana would be grown under licence from the federal government under a legalisation plan to be introduced to parliament next week by three MPs from the major parties and Greens.

Under the bill, a new regulator separate from the Therapeutic Goods Administration would oversee the growing and supply of medical marijuana and determine the conditions for which it could be prescribed.

The bill will be jointly backed by three MPs from a cross-party working group on drug policy: Green Richard Di Natale; Labor's Melissa Parke and Victorian Liberal Sharman Stone.

"Let's be grown up about this," said Ms Stone. "We should allow those currently suffering cruel deaths to have access to medicinal cannabis.

"It isn't new. It isn't innovative. It's just Australia catching up."