The New South Wales Young Nationals has expelled one member and suspended two others after revelations the group had been infiltrated by members of Australia’s alt-right movement.

On Sunday the ABC’s Background Briefing revealed that members of the NSW Young Nationals were members of the Lads Society, a far-right fight club whose leaders include the prominent alt-right figure Blair Cottrell.

The Young Nationals – including one member of the party executive – were or had also been members of a Facebook group called the New Guard, whose followers include self-described fascists.

Membership to the party’s youth organisation has also been temporarily suspended.

On Monday the deputy premier and leader of the NSW Nationals, John Barilaro, admitted his party may have been an “easy target” for members of the far-right seeking to influence mainstream politics.

“We are a grassroots party that is brought together by geography so I think we are probably an easy target,” he told ABC radio. “If you want to become a member and then start bringing more members in, we are a small party so a small number of members joining can actually change the structure of a branch or an electorate council as we call them.

“So maybe it’s because we are an easy target for individuals to infiltrate.”

Barilaro admitted the reports were “worrying”, saying there was a “question mark” over how influential the members identified by the ABC had been in developing policy within the party’s youth wing.

He downplayed the significance of the group on the wider party.

“The Young Nationals are of course a voice for young Australians who want to be part of the democratic process in politics and they have an opportunity to influence, I suppose, party policy,” he said. “But they are only a very, very small part of our party.

“Our policy positions are always endorsed at conference annually around the state [and] the Young Nationals would only represent a very small number [of members] at best.

“The reality is, can they influence policy? No. But they can get on the floor and debate issues and at times that can be embarrassing for the party.”

The former deputy prime minister and Nationals leader Tim Fischer, speaking to ABC Sydney, blamed the rise of the alt-right in Australia in part on social media helping groups build networks as well as “people falling between the cracks” of economic growth.

“They have an agenda which is poison, which is toxic, at a time when we want unity of purpose in this country,” he said. “All I can say is as parliament resumes our colleagues down there in the Nats room will be discussing this and making sure it’s dealt with at another level.”

The Lads Society was founded last year, renting an office space in Cheltenham, a suburb in Melbourne’s south-east. It has since expanded to Sydney, where it also meets in an undisclosed location.

It describes itself as a “traditional-style men’s fraternal society” but is the latest project for former members of the defunct far-right group the United Patriots Front, including Cottrell, its former leader.

The group hosts regular fight clubs and posts videos of the meetings online.

The Background Briefing investigation revealed three members of the Young Nationals had attended the meetings, while other members of the party had racist in-jokes containing coded references to Hitler, and theories of a global Jewish conspiracy related to the alt-right movement.

In a statement on Saturday, the Young Nationals said “radical ideologies have no place” within the party, and announced they would carry out an “urgent investigation” headed by the party’s constitution and ethics committee.

“Allegations regarding the infiltration of the NSW Young Nationals by ‘alt-right’ and/or ‘far-right’ persons or groups is of the [utmost] concern to the NSW Nationals,” the statement read.