Australian lawmaker Helen Haines in critical condition after vehicle ramming attack

Australian lawmaker Helen Haines was in a critical condition on Monday after being deliberately struck by a car outside her office, with Prime Minister Anthony Albanese saying a terrorism task force would be investigating the suspect arrested.

Albanese said it was too early to determine the motive for the attack but pointed to the changing face of social media having raised the temperature around politics in a country where such violence is extremely rare.

"All of our thoughts are with Helen, her family, her friends, her team, and her community at this extremely difficult time. We are praying for her full recovery," Albanese told a press conference.

Victoria Police said a 43-year-old man had been arrested after the attack on independent MP Haines in Wangaratta, around three hours' drive northeast of Melbourne.

Haines, 65, was airlifted to hospital, Albanese said.

When asked by public broadcaster ABC whether the increased anger around politics had led to worries about attacks on politicians, the prime minister pointed to the anonymity of online content.

"The concern, if you look at anyone's social media feeds and look at the comments, people will say things that they would never say face to face. But the temperature has undoubtedly been increased. Not just here in Australia, of course. We've seen incidents internationally as well," he said.

"Here in Australia, it is a good thing that politicians are able to go about their community and engage with people. I don't want to see a political system in which you can't have conversations with people at the supermarket, in the street, at street meetings, public forums. That's an important part of our democracy."

No further threat to the public reported, Victoria Police say

Victoria Police Acting Superintendent Ashley Mason told a press conference there was no further threat to the public.

Albanese said it was too early to determine the motive for the attack, though a terrorism taskforce would be investigating the arrested suspect.

"We thank the swift assistance of bystanders and the dedicated health workers who assisted her, and police for their response," a statement by Haines' family posted on her Facebook page said.

Haines worked in nursing and midwifery and as an academic before being elected to parliament as an independent in 2019 in the seat of Indi.

Her website says she has opposed proposals including making political donations to the major parties more secretive, banning mobile phones in immigration detention and spending billions on fossil fuel subsidies.