Christchurch Police are warning members of the public not to be taken in by scammers asking for cash to buy petrol.

Christchurch Central Area Commander Inspector Derek Erasmus says Police have received multiple reports of people being approached by individuals claiming they need cash to buy petrol so they can get home.

"In the vast majority of cases, these people are scammers and the plea for money is a deception," he says.

"We have had a reports of people being approached in mall car parks, but more recently also in the central city.

"These scammers may be operating anywhere across the city.

"Our advice to anyone who is approached is simple - don't give cash to strangers. Ignore the approach and report it to Police - and if you can, note down any descriptions and vehicle registrations."

Inspector Erasmus says one prolific offender, who is known to Police, is a Caucasian man in his 40s, clean-shaven, with missing teeth. He typically poses as a farmer from Hororata, and asks for money as he has run out of petrol.

"There may be other individuals running the same ruse - it's a well-known scam.

"They are clearly successful as the scam is continuing, and on a scale where they are believed to be making significant sums of money."

Inspector Erasmus says Police are continuing to investigate reported incidents and will look at possible prosecutions for obtaining money by deception, which is punishable by prison terms of between three months and seven years.

Anyone with information is asked to contact Christchurch police on (03) 3637400.