Police investigating the attack on federal MP Helen Haines are exploring whether it may have had something to do with a reported rift between accused man Brendan Nugent and his family.

Haines, the independent member for Indi, had to have both legs amputated after being critically injured when 43-year-old Nugent allegedly deliberately struck her with his four-wheel drive outside her Wangaratta electorate office on Monday.

She remains in a critical condition in Melbourne’s Alfred Hospital.

Nugent faced court on Tuesday charged with dangerous driving causing serious harm, intentionally causing serious harm and causing harm to a Commonwealth public official.

Victoria Police Commissioner Mike Bush, who has previously said police are not ruling out further serious charges, told ABC Radio Mildura on Friday that Nugent’s father Rod and Rod’s partner Christine Cunningham were cooperating with investigators and had been “very, very helpful”.

Asked if one line of inquiry was that Brendan Nugent’s alleged attack against Haines was a “proxy” for attacking his family, Bush said: “Yes it is.”

“It sounds like a cliche, but every line of inquiry is open,” the commissioner added.

The Australian earlier also reported it had been told by multiple sources that police were focussing on Nugent’s alleged “hostility” towards his father and stepmother as they looked for a motivation for the alleged attack.

Rod Nugent and Christine Cunningham released a statement on Tuesday saying Haines had been their friend for more than 20 years, and they would be “assisting Victoria Police in any way we can”.

“What happened to her yesterday is devastating and unfathomable,” they said.

Bush told the ABC that Nugent’s interactions with neighbours were also being examined.

The shocking incident has shone a spotlight on MP security measures more broadly and the increasing number of threats against politicians, with Australian Federal Police Commissioner Krissy Barrett describing the current criminal threat environment as “febrile”.

Federal Communications Minister Anika Wells has shut her office after an incident on Wednesday.

“Unfortunately, I’ve been advised we need to close the office temporarily while security improvements are made,” Wells said in a statement on Friday.

“Our staff deserve to feel safe at work and this kind of behaviour is unacceptable.”

Queensland Police charged a 47-year-old Nundah woman with public nuisance over the incident.

Anika Wells has shut her office after a security incident. Photo: Mike Bowers

Federal Energy Minister Chris Bowen urged members of the public to leave politicians alone, regardless of which party they belonged to.

“Whether it’s ‘stone them in the square’ or whether it’s Warren Mundine, frankly, telling jokes at CPAC about bashing me up, physical violence to me, it’s not funny,” he told News24. “Every Australian in politics is doing a job, plenty of people I disagree with, but they’re fine Australians, just going about trying to do their job. No one deserves violence.”

Bowen was referring to Question Time comments by Liberal MP Angie Bell suggesting Small Business Minister Anne Aly should be “stoned and shamed in public”.

Former Liberal party candidate Warren Mundine joked at the conservative CPAC conference earlier in October that a friend had admonished him not to murder Bowen after bumping into him in Canberra.

A man was also charged in Western Australia this week for allegedly making threats and wielding nunchucks in the electorate office of state Labor MP Hannah Beazley.

The nation’s police forces, Home Affairs department and state leaders have moved to crack down on security and offer briefings.

In NSW, some parliamentarians who attended a state police-run briefing said they were left with broader concerns about their safety and felt examples given were politicised.

They were told to monitor their surroundings closely and alert NSW Police to their movements. An app for a beacon to alert police of safety concerns was also encouraged.

Victorian politicians also received a security briefing. A second briefing for those unable to attend will occur on Friday night.

Federal parliamentarians have also been briefed on keeping themselves and their staff safe.

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–with AAP