Two northern NSW resident action groups campaigning against NBN towers have sent blood sample results to NBN Co and its contractors in a bid to scare them off their rollout plans.

The groups - the Friends of Condong Ridge, which opposes a tower at Clothiers Creek, and the OREAD Project in Kyogle shire - say they have taken a leaf from the book of anti-cell tower campaigners in Wales.

Under the strategy, residents take a blood test before a cell tower is erected and send the results with a legal liability letter to the telco, its contractors and the land owner hosting the tower.

The letter states that further pathology tests will be undertaken once the tower is in place, and threatens litigation if any trend is uncovered between the 'before' and 'after' tests.

Both NSW groups say a dozen residents in each area have taken the blood tests.

Friends of Condong Range spokesperson Josh Bloom told iTnews the group had sent its blood tests and liability letter to NBN Co, Visionstream and the land owner's lawyer three weeks ago.

"We had the lawyer write a liability notice basically stating that the blood tests will be redone after the tower is installed and if there's any trend change across the group, then liability will rest with you," Bloom said.

"It would have to be a trend because if it was only one person, it could be argued that any number of factors can cause someone's blood to change.

"But if we find a trend across a dozen people or more that's out of the ordinary and we can prove that, then we can attribute that to the common thing, being the tower."

Bloom's group has been fighting a proposed tower installation since August 2014.

OREAD Project founder Ammun Luca told iTnews his group was fighting NBN towers in the Tweed Caldera area.

He said they had submitted a dozen blood tests to NBN Co and fixed wireless builder Ericsson.

"As far as we know there's no one else in Australia that's done this besides our two groups," Luca said.

An NBN Co spokesperson did not comment specifically on whether or not it had taken receipt of the blood test results, but told iTnews that the company's network "is designed and operated safely and responsibly."

"NBN Fixed Wireless equipment is designed to fall well within the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) limits as recommended by the World Health Organisation," the spokesperson said.

Blood tests represent a dramatic escalation in the avenues of opposition at the disposal of residents groups, who have typically used grassroots political action and pressure on councils to stop or shift the location of tower projects.

Despite appearances, Bloom said his group was not against the rollout of fast internet.

"We're pro fast internet but we don't believe fixed wireless is a good technology," he said.

Bloom noted that when the fixed wireless contracts were awarded in 2011, fibre-to-the-node (FTTN) was not a rollout option as per the previous Labor Government's majority fibre-to-the-premise approach.

However, Clothiers Creek has existing copper connections, and Bloom said he wanted to test their feasibility to carry internet services that could be much faster than fixed wireless.