At a Tamworth screening of medicinal cannabis documentary High As Mike last week, the New England MP was accused "of not understanding the issue".

Mrs Haslam claims the embattled MP told her he "had better things to do than watch this f****** movie", and that she "didn't have a monopoly on grief", following the death of her son, Dan, to bowel cancer in 2015.

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Mr Joyce's brother, Tim, also recently died as a result of bowel cancer - a fact that Mr Joyce repeatedly alluded to during the robust discussion with Mrs Haslam, and members of the crowd, following the film.

Back in 2016 the New England MP was a vocal supporter of Ms Haslam and her efforts to make the drug more accessible for chronically ill patients, even congratulating her in writing. Mr Joyce is on personal leave and could not be contacted.

But in a letter to Ms Haslam from March 3, 2016, he wrote "it was indeed wonderful to see the medicinal cannabis legislation recently pass through the Federal Parliament".

"Your work and advocacy has been truly outstanding and this outcome will be of enormous benefit to many people and their families facing the courage of cancer and other illnesses for many years to come," he wrote.

"Once again, well done Lucy and I know the community will be forever grateful for the work that you have undertaken. As always, if there is any way I may be able to be of assistance, please don't hesitate to contact me."

A month later, at the farm's opening, the then Acting Prime Minister was again supportive.

"When you can find a use for any part of a plant that can assist people when they are ill, when they are in pain, you should do it," Mr Joyce said. But now it seems to be a different tune the New England MP is singing.

His change in position became evident last week at a screening of the documentary, when he was accused of swearing at Ms Haslam - something Mr Joyce denied doing - and telling her she did not have a "mortgage on grief" - which he did not deny saying.

Mr Joyce's brother Tim passed away from bowel cancer in mid-2018. It's the same disease that claimed Ms Haslam's son, Dan, in 2015.

"That does not mean for one second that there is some grand elixir or ... that there is some hope that somehow my brother Timothy would be alive if this happened. I get furious with that," Mr Joyce said during the theatre exchange.