Rhett Wallace and Cassie Batten leaving the Epping police station. Credit:Joe Armao

The family is one of at least 150 around the country reported to have turned to the oil, which is advertised by its supplier as having so low a dose of tetrahydrocannabinol, the psychoactive ingredient in cannabis, that it is not illegal. In their letter, the MPs cite the case of Mr Haslam, 24, who uses cannabis to treat the nausea associated with the chemotherapy he is receiving for bowel cancer.

''None of the conventional medicines relieved his distressing symptoms. But medicinal cannabis did,'' the MPs wrote. ''If Daniel was part of your family, wouldn't you want him to be able to use cannabis as a medicine in his last moments of life when everything else had failed? And if you would want that for you or one of your loved ones, why wouldn't you also want that for someone you don't know?''

Mr Haslam's mother, a retired nurse, and his father, a former drug squad detective, have campaigned for marijuana legalisation since seeing its benefits for their son, and have received support from their local police chief and local MP, federal Nationals Agriculture Minister Barnaby Joyce.

In their letter to Dr Napthine, the MPs write: ''We are of the view that the police raid on Ms Batten's home was inappropriate and contrary to existing community values and views on this issue.