Errant retailers at Sim Lim Square often offer what seems like a good deal. But after the money is paid and a sales agreement is signed, the retailer will demand more money for "extras" such as warranty services.

If the consumer declines, they are forced to give up both the goods and their initial payment.

This practice runs afoul of consumer laws here, said Consumers Association of Singapore (Case) executive director Seah Seng Choon.

He said: "If the total cost of the item is not disclosed before the consumer signs the sales agreement, it is a breach of the Consumer Protection (Fair Trading) Act (CPFTA)."

Mr Seah advises consumers to do research in advance.

"Consumers can consult local web forums to get feedback on the retailers, the average cost of the product, and other issues like after-sales service, warranty fees, common defects etc," he said.

Case also puts out a list of errant retailers online and at two shopping malls - People's Park Complex and Sim Lim Square.

Both Mobile Air and Cyber Maestro are on the consumer alert list for having the most number of complaints over the past three months.

The management council of Sim Lim Square revealed on Monday that consumers were often at the losing end when dealing with errant retailers.

"Frequently, it would be the retailer who calls the police and accuses the aggrieved customer of causing a scene at the shop," it said.

A spokesman for Sim Lim told The Straits Times earlier this week: "As Sim Lim Square is a strata title building, we are not the landlord; we are only the managing agent, so we are not able to kick the tenants out."

Consumers who cannot settle a dispute with retailers can approach Case, and tourists can contact the Singapore Tourism Board.