FILE PHOTO: Bayer's Roundup weed killer atomizers are displayed for sale at a garden shop near Brussels.

Melbourne - A gardener with cancer has launched Australia's first legal action against global agribusiness giant Monsanto, owned by Bayer, over its popular Roundup weedkiller.

Michael Ogalirolo, 54, was diagnosed with non-Hodgkins lymphoma in 2011 after regularly using the herbicide for his work as a self-employed landscape gardener over an 18-year period, the Sydney Morning Herald reported on Tuesday.

The lawsuit, filed at the Victorian Supreme Court on Monday, alleged Monsanto Australia failed to warn users that Roundup products are dangerous to human health, including that they cause cancer.

Glyphosate, the active ingredient in Roundup, has been linked with cancer after a finding by the International Agency for Research on Cancer in 2015.

Bayer, the German parent company of Monsanto, said it was aware of media reports but had not received a writ of the Australian case. 

"We have great sympathy for any individual with cancer, but the extensive body of science on glyphosate-based herbicides over four decades supports the conclusion that Roundup does not cause Non-Hodgkin's Lymphoma (NHL)," Bayer said. 

It said extensive studies by scientists and regulators found that glyphosate "is not carcinogenic" and the company will stand by its "products and will vigorously defend them".

But Sanchia Aranda, the chief executive of Cancer Council Australia, said people should avoid the use of glyphosate products "if it is not necessary and those who do need to work with it should take proper health and safety precautions."

In May, a jury in California awarded a US couple a payout of $2 billion after ruling that Roundup caused them to fall ill with cancer.