Unlicensed tradespeople claiming to have leftover bitumen from a previous job are approaching home and business owners and offering to do cheap work.

However, the work done by these 'bitumen bandits' is substandard and consumers are often left out of pocket as they struggle with the cost of remedial work to fix the mess left behind.

Commissioner for Consumer Affairs Dini Soulio cautioned people against accepting offers of work from people going door to door.

"People should never accept an offer from someone going door to door, without doing their research first," Mr Soulio said,

"Seek multiple quotes, look for testimonials and if the trader is using high-pressure tactics to try and force a sale, don’t engage."

Consumer and Business Services has recently received 12 complaints from consumers who have been approached by these unscrupulous operations, with reports from Stirling North, Mallala, Athelstone, Renmark, Murray Bridge, Ceduna, Dry Creek, Mile End, Melrose Park, North Plympton, St Marys and Lonsdale.

Consumer and Business Services is working with state and federal agencies, including the South Australian Police and Border Force, to identify the bitumen bandits and gather evidence of their offences.

Anyone who has encountered these offenders is encouraged to contact Consumer and Business Services by calling 131 882 or report them online as quickly as possible, as part of the challenge is that the bandits often move location before a complaint is received.

Consumers can also check with Consumer and Business Services whether an individual has a current and valid licence.

People who perform building work unlicensed are liable for an up to $50,000 fine. The maximum penalty for a breach of Australian Consumer Law is a $2.5 million fine.