Independent MP Dr Helen Haines is fighting for her life in hospital after she was mowed down by a 4WD outside her electorate office in regional Victoria.

Visibly shaken Prime Minister Anthony Albanese said the “attack” on the federal member for Indi “wasn’t an accident” but a “deliberate act”.

Haines, a mum of three and grandmother, was struck by the Toyota Land Cruiser in the rural town of Wangaratta, in Victoria’s north, on Monday afternoon.

A bystander performed a citizen’s arrest on the 43-year-old male suspect who is now in custody as counter-terrorism authorities investigate.

A knife was seized from inside the man’s vehicle.

Haines, 65, suffered critical injuries and was set to receive further treatment after being airlifted to The Alfred hospital in Melbourne.

She was in a critical condition fighting for her life on Tuesday morning after undergoing emergency surgery.

Authorities are yet to determine the motive for the attack or establish whether the suspect, from the nearby town of Tarrawingee, is known to Haines.

The incident has been condemned by political leaders including Albanese, who said there was no place for political violence in Australia.

“This wasn’t an accident. There was a deliberate act, it would appear,” he told the ABC’s 7.30 program.

“We don’t know what the motivation is. So that is the work that’s being undertaken.”

It is the most serious in a string of threats and alleged attacks on politicians in the last year.

Nationals MP Sam Birrell, whose electorate of Nicholls neighbours Haines’ seat of Indi, said the pair had remained friends despite political differences.

He said the attack could be a turning point for how regional MPs interact with their communities.

“I’m sure the AFP will speak to us in the next 24 hours or 48 hours, and I think that there’ll be a little bit of a shake-up of the way we do things,” he told the ABC.

“Many of us in regional communities go and advertise that we’re going to be in a certain place … the idea is in Australia, you represent your people. You want to hear from them.

“I don’t want to see that lost, but obviously we need to understand what’s happened here and whether there are things that we need to do.”

Albanese said the political landscape had changed drastically in the 30 years since he was first elected to parliament.

“There has been too much shouting, not enough discourse, not enough polite conversation and disagreement,” he said.

“In a democracy, we should be able to have discussion, political debate, put different views forward, but do it in a way that is respectful.”

Haines was a beacon of light in northern Victoria and federal parliament, the prime minister said.

“There’s a reason why Helen Haines is so loved and admired, because she’s someone of integrity. She’s someone who treats everyone with respect,” he said.

Albanese said he was not personally aware of prior threats toward Haines, but his parliamentary colleagues regularly spoke about rising threat levels across the nation.

-with AAP