A RADICALISED white supremacist who expressed an intention to commit a mass shooting at a popular shopping centre had previously been arrested in Toowoomba.

Michael James Holt, 26, has pleaded guilty to firearm manufacture and possession after a search by police discovered weapons across three properties in 2015.

Holt was arrested in September 2015 following a tip-off in July to the Firearms Squad that he had bee manufacturing homemade guns, knuckle dusters and slingshots.

He was caught and charged by police just a month later after he attended the Big Show Militaria, Guns Collectables Fair at the Toowoomba Showgrounds.

Holt had been carrying a knife and knuckledusters at the event which sees dealers from all over Australia sell antiques, swords, guns, military items and collectables.

Holt had been stockpiling the weapons across Sydney and expressed an intention to conduct the mass shooting at a Westfield shopping centre there.

He will be sentenced in March.