Tasmanian Labor Senator Helen Polley made the claim on Twitter after speaking to the farm owner at Evandale in the state's north.

A spokesperson for the former prime minister said Mr Morrison had no knowledge of the matter and would never have made such a request.

"It is an extraordinary revelation and it needs investigation because the idea that he would have a dunny built for him before a visit beggars belief," Senator Polley said.

The farmer - who preferred to remain anonymous - indicated the infrastructure "suddenly appeared in the middle of nowhere without any communication" the week Mr Morrison was set to make an appearance there.

He was hesitant to make a definitive claim but said the timing of the works was "hard to overlook"; however, he also felt the two events crossing over could have been merely coincidental.

Ownership of the outhouse was also shrouded in controversy. The property owner had sold off a portion of the land to Tasmanian Irrigation several years ago and was unsure if the structure crossed over his land border.

"Tasmanian Irrigation could have constructed it, as they built a dam on the land they bought, but their staff probably only come here about six times a year, and the toilet is a fair trek from the dam," he said.

The borders of the two separate patches of land weren't the only dividing lines in question, as the property itself crossed the boundaries of two different municipalities - The City of Launceston (CoL) and the Northern Midlands Council (NMC).

According to members of each council's planning team, no application matching the works undertaken on the site showed up on any records for that address.

A CoL representative said approval was granted to TI for two subdivisions on the property, the construction of a quarry, the implementation of an extensive irrigation pipeline, and the building of a pump station.

No outhouse was mentioned, however, they said a toilet block could have been included in any of the approved works, but further investigation was required to determine that.

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A NMC spokesperson said if the planning scheme had been breached, a retrospective application would need to be lodged and then assessed. They also noted that an application would only be required if the outhouse was above 2.4 metres tall and closer than 30 metres to a wetland or watercourse.

A TI spokesperson said a purchase order was raised for the construction of an outhouse in November 2018 and works were completed in January 2019 for $10,200 on TI-owned land.

They said the site was a safe distance from all watercourses, approximately 40 metres downstream of the dam wall and built for employees who inspect the site three times a week.

Mr Morrison visited Northern Tasmania in February 2019.