An Australian politician is fighting for her life in hospital, and has lost one leg, after an allegedly deliberate attack in broad daylight.

Helen Haines, 65, an independent member of Australia’s lower house of parliament, was hit by a car mid Monday afternoon, local time, in what the Prime Minister, Anthony Albanese, called “a deliberate act”.

According to eyewitnesses, the Toyota Land Cruiser performed a U-turn, drove into a car parking area outside Haines’ constituency office in the regional town of Wangaratta in Victoria and hit her twice, pinning her against her car.

The former nurse, mother of three and grandmother suffered “severe” lower-body injuries.

Onlookers rushed to her aid while Ricky Jefferies, a barber working next door, pulled the driver from the car. Jefferies said he had “no choice” but to take action “because it was the right and safest thing to do”.

He said he pulled a knife from the man’s pocket and threw it aside.

Albanese said Jefferies’ actions were a reminder “that at the worst of times we see the best of the Australian character… even in dark times we see light”.

The Australian federal police commissioner, Krissy Barrett, said a 43-year-old man from nearby Tarrawingee was in police custody. She said at this stage it appeared to be an isolated incident “and there are no known threats connected to this matter”. No charges had been laid at the time of writing.

The alleged attacker was identified in Australian media as a man with a history of anti-Israel and pro-environment social media comments, who was reportedly involved in anti-forestry campaigns. His only interactions with Haines online were mild and included praising her position on environmental issues. Haines has voted consistently for parliamentary motions expressing concern over Israel’s actions in Gaza, and for stronger climate action.

The incident comes amid growing concern in Australia over threats and intimidation aimed at politicians. Since October last year, 41 people have been charged in relation to threats against federal parliamentarians and high office holders, according to federal police.

Many of those targeted were women. The head of Women for Election, Licia Heath, told Australian radio that nearly 90 per cent of women who hold elected office, or who are running for office, have experienced online abuse or intimidation linked to their political participation.

“We’re not talking about harmless trolls,” she said. “We’re talking about ongoing death threats, 600 threats coming in an hour, threats against children and family, rape threats, rape threats against children.

“We knew from peer organisations overseas that what they were suffering is that online abuse threats were increasingly becoming real world violence.”

Almost two-thirds of the respondents to the Women for Election survey said it made them less likely to run.

Albanese warned that it was too early to know the motivation for the attack. He said there was “a lot of speculation at times like this” but added that “it is clear that this was a deliberate act because of the nature of what occurred”.

An emotional Albanese paid tribute to Haines as a “much admired and respected” politician.

Haines was flown 250km to Melbourne where she was said to be in a critical but stable condition, with doctors performing multiple surgeries. Local media reported that she had lost her leg, and doctors feared she may lose the other one.

Haines is best-known for her fight to establish a national anti-corruption body. She is considered one of the most effective and experienced members of the country’s recent crop of unaligned politicians who won power through grassroots, community movements.

Her influence on public policy was demonstrated when colleagues made T-shirts reading: “What would Helen do?”

Fellow independent Zoe Daniel wrote after the incident: “Helen is the one you go to when you’re grappling with the moral quandaries that arise frequently as an MP, in a job when a binary yes/no vote sometimes feels impossible. With intelligence, warmth and deeply held ethics, she represents the very backbone of the parliament.”