A woman wearing a One Nation shirt was allegedly left with a broken rib after an assault at the Ekka, according to the party, which said it would change its policy on volunteers wearing branded clothing in public.

The woman was described by One Nation as a 63-year-old grandmother who was volunteering at the party’s stall at the annual show in Brisbane.

Speaking on 4BC on Monday, Hanson’s chief of staff and party spokesperson James Ashby said the woman was approached by four young people near the gates of the showgrounds, when one swung her around by the arm and punched her in the ribs.

“She now has one broken rib, she’s got enormous bruising, and she’s had to go through the unedifying process of having to strip down in front of police so they can take photographs,” he said.

Ashby said the group was made up of three young women, who spat on the volunteer, and a male who hit her.

He said police were investigating the situation and “trying to track these people down”.

This masthead has been unable to verify the victim’s identity or the details of the assault.

A Queensland police spokesperson said no formal complaint had been made.

“Police are aware of an altercation at Brisbane Showgrounds, Bowen Hills on 14 August,” they said.

It is not unusual for police to make inquires about a potential assault without a formal complaint, as potentially crucial evidence such as witness testimony or video can be lost if a complaint is made later.

One Nation senator Barnaby Joyce spoke about the incident with Ben Fordham on Sydney radio station 2GB, linking it to national protests against One Nation and its leader on Thursday.

Ashby also drew comparisons between the protest and the alleged incident at the showgrounds.

“[The victim] said they were the same kinds of people that we saw the day before in those street protests students attended,” he said.

“I don’t know what Thursday’s actions brought, but it brought about this ... confidence from young people that they can attack people on the conservative side of politics.”

Ashby said the woman had been discharged from hospital over the weekend.

He said One Nation had changed its policy about wearing party merchandise in public.

“Our people are not allowed to wear uniforms any more outside of their work conditions ... I do fear for where things are going in this country because the left don’t know how to deal with conservatives,” he said.