By Zac de Silva in Canberra

Former SAS soldier turned federal MP Andrew Hastie is batting away criticism from the girlfriend of accused war criminal Ben Roberts-Smith, refusing to be drawn into an online stoush.

Sarah Matulin, who met the Victoria Cross recipient while they both worked for media giant Seven West, took aim at Mr Hastie in a comment on Instagram.

Ms Matulin wrote “yeah you’re a traitor” underneath a post of Mr Hastie and his children on Anzac Day, which had a caption about the importance of remembering fallen soldiers.

Her comment was later deleted.

In a statement through Roberts-Smith’s lawyer, Ms Matulin conceded the online remarks were an error.

“It was a mistake to make that comment in a public forum and wasn’t done with Ben’s knowledge,” she said.

Asked about the comment, Mr Hastie struck a philosophical tone.

“It is what is is, and I really have nothing to add to it. Life goes on,” he told Sky News on Tuesday.

“I’m just very cautious, given that a fair trial, the presumption of innocence and a few other legal principles are at stake here, so I won’t be commentating like other public figures on this,” Mr Hastie said.

When Roberts-Smith sued for defamation over a series of newspaper articles accusing him of war crimes, Mr Hastie was called as a witness by Nine Entertainment, the publisher defending the suit.

The now-Liberal MP was a captain in the SAS for more than five years and was deployed to Afghanistan alongside Roberts-Smith.

Mr Hastie said he may be called as a witness in the upcoming criminal trial.

Roberts-Smith has been charged with five counts of war crime murder over a series of alleged killings in Afghanistan.