Police probing family rift, Brendan Nugent's interactions with neighbours in Helen Haines attack investigation

Victoria's police commissioner has confirmed that a reported rift between Brendan Nugent and his family is one line of inquiry as officers investigate Monday's attack against federal MP Helen Haines.

The commissioner stated that Mr. Nugent's family had been "very, very helpful" to their ongoing investigation into Monday's attack on Helen Haines.

Asked if one line of inquiry was that Mr. Nugent's alleged attack against Ms. Haines was a "proxy" for attacking his family, Victoria Police Commissioner Mike Bush said "yes it is."

"It sounds like a cliche, but every line of inquiry is open ... Every action is under review," he said.

The commissioner's comments come as Ms. Haines remains in a critical condition at The Alfred hospital in Melbourne, with hospital staff set to provide another update on her condition.

Commissioner Bush said the 43-year-old's father Rod Nugent, and the father's partner Christine Cunningham, had been "very, very helpful" to the police investigation.

The couple released a statement earlier this week in which they said they had been friends with Ms. Haines for two decades, and described Monday's events as "devastating and unfathomable."

"We will be assisting Victoria Police in any way we can," they said.

Commissioner Bush said the couple were "absolutely cooperating."

He also stated that Mr. Nugent's interactions with neighbours were being looked at and that the actions of local police who received those neighbour complaints would be examined.

"They are wonderful people, our police in Wangaratta, they come to work every day and every night to do the best," he said.