Opposition Leader Bill Shorten has partly explained the presence of a dog at Labor backbencher Emma Husar's office, saying it was her son's therapy dog.

Key points: Emma Husar took personal leave after referring violent threats against her to police

Emma Husar took personal leave after referring violent threats against her to police Former staff have accused Ms Husar of bullying

Former staff have accused Ms Husar of bullying Simon Birmingham says Bill Shorten must take personal responsibility for investigation

NSW Labor is investigating complaints against Ms Husar including bullying and asking her staff to perform personal duties while working in her electorate office.

Channel Seven last night showed vision of one of Ms Husar's staff walking the dog and picking up after it.

Today Mr Shorten said one of Ms Husar's children had autism and the animal was a part of his therapy and treatment.

He did not explain why the dog was at Ms Husar's Western Sydney electorate office.

"I don't know all the circumstances, I wouldn't ask you or anyone else to pick up my dog's poo, but I wouldn't ask you or anyone else to pick up my dog," he told journalists today.

Ms Husar took personal leave effective immediately on Tuesday evening, revealing she had referred violent threats against her to the Australian Federal Police.

Mr Shorten said Ms Husar was a "good person going through a very tough time".

"Emma has been through a pretty difficult family law process," he said.

"There sounds to be a lot of internal family turmoil here".

He said that did not excuse any waste of taxpayer money and emphasised that people were entitled to respectful workplaces and treatment.

Channel Seven last night showed vision of one of Ms Husar's staff walking the dog. ( Supplied: Channel 7 )

Government seizes on issue ahead of by-elections

Earlier a senior Cabinet minister called on Mr Shorten to sack Ms Husar if the bullying and harassment allegations against her are proven.

Education Minister Simon Birmingham said any threats of violence against Ms Husar would never be appropriate, but called on Mr Shorten to take personal responsibility for the investigation.

"If any of the allegations are true, then Emma Husar has no place on Bill Shorten's team," Senator Birmingham said.

"He should go to Sydney and dismiss her as an MP, disendorse her as a candidate and ensure that he takes responsibility for a member of his team where the allegations are clear, that they have been doing the wrong thing with their taxpayer funded staff."

Emma Husar said she had received threatening messages, including threats of violence.

Earlier Ms Husar said the last few days had been incredibly difficult for her family and she wanted to step out of the spotlight to get support.

"I'm a single mum and my first priority is the safety and wellbeing of my children," she said.

Ms Husar has previously said she was horrified to learn of the misconduct investigation and said the allegations did not reflect who she was or how she ran her office.

With crucial by-elections on Saturday, Senator Birmingham called on Mr Shorten to return to Sydney to speak with Ms Husar's former staff and ensure a thorough investigation.

Simon Birmingham says Ms Husar has no place on Mr Shorten's team if the allegations are true. ( ABC News: Matt Roberts )

"Emma Husar is a Labor MP who Bill Shorten has campaigned alongside of, she is now seriously alleged to have abused taxpayer entitlement, to have abused and misused her staff, to have exploited workers," Senator Birmingham

said.

"Bill Shorten has spent his career saying he cares about worker exploitation. Well if he does, has he spoken to Emma Husar's staff? Will he go and meet with them?"

NSW Labor said it had an independent process for assessing complaints, which would provide advice on how to respond to the allegations.

A party spokesman said no public comment would be made during the course of any independent assessments, but said "comment may be made at the conclusion of the independent process".