A Byron Bay physiotherapist is being harassed by anti-vaccination campaigners who have mistaken him for a pro-immunisation blogger known as Reasonable Hank.

The activists, who run the Anti-Vaccination Australia Facebook page and the Septic Skeptics website, believe they have unmasked Reasonable Hank whose real name is reported to be Peter Tierney.

However, the activists have mistakenly targeted Peter Tiernan.

Mr Tiernan said the case of mistaken identity began two weeks ago when his wife received a message on Facebook from someone saying "I'd like to talk to you about your husband".

The person also tried to contact Mr Tiernan, his 14-year-old daughter, some of his friends, and other family members on Facebook.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 10 minutes 54 seconds 10 m Peter Tiernan mistakenly targeted by anti-vaccination activists ( ABC North Coast: Joanne Shoebridge ) Download 5 MB

Mr Tiernan then started receiving phone calls and text messages from unknown numbers and callers accusing him of being the blogger Reasonable Hank.

Mr Tiernan said it was the first time he had heard of the blogger, so he began searching for him on Facebook.

He became alarmed when he saw threats against Reasonable Hank being posted online.

"They were sending messages to him using my profile picture from Facebook and saying 'We know who you are'," Mr Tiernan said.

"They told him if he didn't take his blog down they would expose me and my family."

Mr Tiernan said his daughter's school had also been named on social media, and photos of him with his family had been taken from his Facebook page and shared by the anti-vaccination campaigners.

Reasonable Hank also provided Mr Tiernan with screenshots of threats that he too had received, including death threats.

"It was more kind of veiled threats, aimed at him, but thinking that I am him," Mr Tiernan said.

Reasonable Hank told Mr Tiernan the comments included knowledge of where Mr Tiernan worked and whether he was at work on a given day.

Mr Tiernan also said the activists had called his workplace.

He has since changed his phone number.

Police investigating

A post on the Septic Skeptics website that purports to unmask Reasonable Hank as Mr Tiernan thanks two activists "who have worked tirelessly over the last few months tracking this slime ball's every move".

Mr Tiernan said he felt like he was being stalked.

I told them [the anti-vaccination people] that it wasn't me; I just felt powerless," he said.

"It's been two weeks of lack of sleep.

"It's probably affected my wife most."

Mr Tiernan said he had filed a complaint with the police, who were investigating the matter, and he was also seeking legal advice.

"I'm not across social media and I've since taken down my Facebook page, but I feel like I've been caught up in the middle of this as an innocent victim," he said.

"I've changed my phone number, closed my Facebook page, and I'm trying to protect my family.

"There's not much more I can do."

The ABC has contacted the Anti-Vaccination Australia group and Reasonable Hank for comment.