Ben Roberts-Smith's partner accused Liberal MP Andrew Hastie - a potential Crown witness in his criminal case - of being a 'traitor', in a post she admits was a mistake. 

The former SAS soldier-turned-politician shared an Anzac Day tribute at the weekend about 'remembering the fallen, honouring our veterans and ADF'.

Ms Matulin then replied: ''Yeah you're a traitor.'

Ms Matulin's comment was soon deleted. 

She later issued a statement, via Roberts-Smith's lawyer Karen Espiner: 'It was a mistake to make that comment in a public forum and wasn't done with Ben's knowledge.'

Hastie was one of 21 SAS veterans subpoenaed as a witness in the failed defamation case Roberts-Smith brought against Nine Newspapers in 2018.

He told the Federal Court he'd heard multiple accounts of the allegation that Roberts-Smith kicked an Afghan detainee over a cliff during a mission in Darwan in 2012.

This allegation makes up one of the five war crime charges currently facing the Victoria Cross recipient. 

Roberts-Smith is alleged to have committed five counts of 'war crime - murder' allegedly committed while serving with the Special Air Service Regiment in Afghanistan between 2009 and 2012.

He is accused of shooting dead one unarmed detainee not taking part in hostilities, taking part in the unlawful killing of a another, and ordering subordinates to execute three more.

Roberts-Smith has consistently denied the allegations.

It is currently unknown whether Hastie will be called on to give evidence during the NSW Supreme Court criminal trial.

Hastie issued a statement to media two days after Roberts-Smith's arrest. 

'In 2022, I was one of 21 SAS veterans of the war in Afghanistan subpoenaed as a witness in the defamation action brought by Ben Roberts-Smith against Nine Media.

'I gave testimony under oath, as required by law. Mr Roberts-Smith is now facing criminal charges in relation to this operational mission, so it is possible that I will be called as a witness to this trial.

Hastie continued: 'I urge every Australian to respect the rule of law, the criminal justice system, and the accused's right to a presumption of innocence and a fair trial. 

'Therefore I will not prejudice this trial by making any further comment.'

Hastie's Anzac Day post also drew ire from disgraced ex-Liberal party staffer Bruce Lehrmann, who was found by a civil court judge to have raped his former colleague Brittany Higgins.

'A most inappropriate post given your complicity in the ongoing public shaming and mudslinging against our ADF,' Lehrmann commented. 

'Your betrayal of BRS and the ADF won't be forgotten.' 

Roberts-Smith and Ms Matulin attended an Anzac Day commemoration at Currumbin RSL on Queensland's Gold Coast on Saturday, where he was seen smiling for selfies with supporters. 

'I've never thought about not coming,' he told the ABC. 'I was always going to be here.'