Taxi passengers have been warned to protect themselves against potential credit-card skimming, after the state's taxi regulator recorded more than 30 instances of fraud by Melbourne drivers last year.

The Taxi Services Commission said complaints about credit-card skimming had gone down, but the threat remained and passengers needed to take care, particularly if they paid using a manual credit card swiper.

A TSC spokesman encouraged anyone who believed their card had been skimmed by a cab driver to report it to the commission.

"Credit-card skimming is a problem impacting all industries," the spokesman said. "The Taxi Services Commission receives complaints about credit-card skimming from time to time, however, we have seen a reduction in recent years, with 33 complaints received in 2013, compared to 52 complaints in 2012."

Dominic Miller, who regularly uses taxis, had his credit card skimmed last Sunday by a driver who said the vehicle's PayPass system was not working and used a second eftpos terminal to take payment. Mr Miller's bank contacted him later that day after a flurry of withdrawals of up to $900 were made on his card, in Sydney. He was in Melbourne at the time.