Liberal frontbencher Andrew Hastie has become a special target for One Nation over his willingness to give evidence against Victoria Cross winner Ben Roberts-Smith, who has been charged with five counts of the war crime of murder.

One Nation used the Roberts-Smith issue in the Farrer byelection, with corflutes declaring: 'He fought for us, One Nation stands with him'.

James Ashby, Pauline Hanson's top adviser and a long term leading strategist in the party, on Tuesday delivered a very direct political threat to Hastie.

'We stand by all of our defence force members, and that is one thing that Andrew Hastie is forgetting,' Ashby said on Sky.

'What I will say to Andrew Hastie is that we've got 430 One Nation members in his electorate [of Canning in Western Australia].

'I did seek the number from our office before coming on air tonight.

'So we're a strong 430 registered, paid up members of One Nation in that seat, and they expect us to run a very strong candidate.'

Ashby said One Nation would stand by Roberts-Smith 'right to the very end, despite what the allegations are.'

He dismissed a rumour that Roberts-Smith (who is subject to strict bail conditions) could run in Canning. 'He's not standing for us, but we will stand by Ben Roberts-Smith.'

Canning was one of four WA seats Pauline Hanson named at the weekend as campaign priorities. The others were Forrest, Hasluck and Pearce.

Hastie, who was in the Special Air Service Regiment (SAS) and served in Afghanistan with Roberts-Smith, gave evidence for the defence in Roberts-Smith's failed defamation case, and expects to be called in a trial.

He has been the target of a ferocious social media campaign for his stand. 

The Roberts-Smith issue has divided former SAS colleagues (some of whom made allegations against him), and also split Liberals. 

The furore has been a major political setback for Hastie, who has his eyes on the Liberal leadership.

Hastie said when Roberts-Smith was arrested that: 'As a qualified member of the SAS, I was present on one of the operational missions in 2012 that was examined by the Federal Court. 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. 

'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 said on Wednesay: 'I don't live in fear of threats made by political operatives.

'My mission is simple: to defeat the Albanese government at the next election.

'If One Nation shares the same mission, why are they targeting a centre-right MP like me? Their strategy makes no sense. Who is pulling the strings in the background?

'I will fight hard, and I won't be deterred.'