WANGARATTA: The man alleged to have critically wounded Australian lawmaker Helen Haines in a "targeted" attack was due to appear in court on Wednesday, as police warned that growing extremism online was fuelling political polarisation.

Haines is in a "critical but stable condition" in a Melbourne hospital after being struck by a car on Monday near her office in Wangaratta, just over 200km northeast of the Victoria state capital, police said on Wednesday.

Police have charged 43-year-old Brendan Nugent with dangerous driving causing serious injury, intentionally causing serious injury and the federal offence of harming a public official, which carries a maximum penalty of 10 years in prison.

The attack has prompted soul-searching in a country where political violence is rare, but where police have documented a steady rise in threats and abuse directed at elected officials in recent years.