The condition of Helen Haines, the Australian MP hit by a car five days ago in north-east Victoria, has improved from critical to serious but stable.

The independent MP, 65, had both her legs amputated after what authorities say was a deliberate attack outside her electorate office in Wangaratta, north-east of Melbourne, on Monday.

In the latest update on Saturday morning, the Alfred Hospital in Melbourne said Haines was in a serious but stable condition, the first improvement since she was airlifted there.

Her alleged attacker, 43-year-old Brendan Nugent, was arrested shortly after the incident and has since appeared in court on three charges.

The politician’s husband, Phil Haines, said on Wednesday that the “horrendous incident” had caused his wife significant injuries but “her heart and her mind” were “in good shape”.

Nugent, who was arrested moments after he allegedly drove his Toyota LandCruiser into the MP, appeared in court to face three charges: dangerous driving causing serious injury, intentionally causing serious injury, and causing harm to a Commonwealth public official.

Police said more charges might be laid, including attempted murder.

His lawyer said his client had “mental health concerns” but did not give any further detail.

Victoria Police has said its investigation, with support from the Australian Federal Police, remains ongoing and a motive is yet to be established.

Investigators are looking into whether drug use or medication played a part in the incident.

Nugent’s family has said they were long-time friends with Haines.

Shortly after the alleged attack, Australian Prime Minister Anthony Albanese told ABC television that there had been a “rise in temperature” and “too much shouting, not enough discourse” in Australia.

Haines, known for stances such as supporting stronger climate action, entered parliament in 2019 after working as a nurse and midwife.