The man, who used the name "John" and claimed to work for "J&J Roofing", is described as having a thick Irish accent and could be part of a larger, co-ordinated group working in the ACT.

Attorney-General Simon Corbell issued the warning on Friday after a Canberra man reported paying several thousand dollars to have roofing work undertaken by the con man.

Only minor work was performed at the resident's house and he has been unable to contact the business.

"Unfortunately, Canberrans continue to be at risk of being ripped-off by people known as itinerant traders, who knock on doors offering a range of services including home maintenance, gardening, bitumen driveway sealing, concreting and house and driveway painting," Mr Corbell said.

"These people take payment in advance but do very little work, if any. They may commence the work straight away but, in most cases, they don't return to complete the job."

The ACT government's Office of Regulatory Services has previously warned about travelling con men working in the ACT.

"Please warn your family, friends and neighbours to be cautious when dealing with anyone who knocks on their door offering a service," Mr Corbell said.

"These people are part of a large group who try to scam as many people as they can before they move on to another part of Australia."

Homeowners have been warned to treat door-to-door salespeople with caution, and to reconsider if they are asking for up-front cash payments, if they turn up unexpectedly and if cheap deals or discounts are only being offered that day.

Mr Corbell said residents should not open the door if they suspected a travelling con man was at their house, and should ask them to leave.

Residents should also record details like a salesman's name and car number plates and should ask for a written contract including a cooling-off period for services costing $100 or more.

"Itinerant traders are brazen and have been known to drive consumers to their bank or an ATM to withdraw cash so they can be paid," Mr Corbell said.

"Don't ever be pressured in this way. The trader may take your money and not do any of the work that was promised."

"While some people work for or operate legitimate businesses that go from door-to-door, a number of people seek to scam residents and take advantage of their trustworthy nature."

Contact the Office of Regulatory Services on 6207 3000 or the National Travelling Con Men Hotline on 1300 133 408.