According to police and the Office of Fair Trading, bands of Irish and English "gypsies" are roaming the country selling "discount" electrical equipment, including generators and high-pressure cleaners, from the backs of white vans.

"This is one of the biggest, best-organised Australia-wide itinerant trader scams that we've seen for many years," the Minister for Fair Trading, Virginia Judge, said.

According to Michael Cooper, the director of compliance at the Office of Fair Trading, "These guys have been going around the country, door to door, town to town, using high-pressure tactics to sell dodgy electrical equipment at way above market price."

Fair Trading said it hopes to prosecute the "rogue traders" - just as soon as it catches up with them.

"There are about 30 to 50 people involved, but they work in separate groups in a very hit-and-run way, popping up all over the country, from Perth to Tamworth, and they can cover hundreds of kilometres in a day."

Len Hanrahan, a wheat farmer from Corowa, near the NSW-Victoria border, got "suckered" three weeks ago.

"These two Irish blokes turned up at my property, totally out of the blue, selling high-pressure cleaners. They were very aggressive and very persuasive," he said.

Mr Hanrahan bought what he was told was a Honda brand cleaner for $1100.

"I'd got him down from $2500, so I thought I had a good deal, until I found out that it wasn't actually a Honda and that the same machine was worth $600 in town.

Mr Cooper, who has been tracking the scam with state police and the Immigration Department, believes the traders are based in Britain.

"They're gypsies," he says. "This is their job. We know from the hotels where they've stayed that they travel in family groups - mum, dad and the kids - like they're teaching their teenagers the family trade."

One group entered the country in July, in dribs and drabs over several days.

Members regrouped in Perth, where they spent more than $100,000 in cash buying generators, air compressors, high-pressure cleaners and fire-fighting pumps.

"Then they hired 12 white vans from different Avis outlets, loaded them up and hit the road," Mr Cooper says.

Ms Judge asked that anyone with information call the Office of Fair Trading on 13 32 20.