SG Vehicles is the first and only motor company to be blackmarked twice by the consumer watchdog, Case said.
Case told The Straits Times that SG Vehicles had chalked up a "high volume" of complaints from consumers pertaining to "misleading claims, false claims and defective goods".
There were 39 complaints against the company last year, up from 36 in 2015. There were nine complaints in the first five months of this year.
Case said the company also operated under names like SG Vehicles Asia, SG Vehicles Continental and SG Vehicles Global.
The company, which operates out of Bukit Merah, was started in 1984, and is run by married couple Mark and Juliet Poh.
Case first flagged the company for unfair practices last year.
Common complaints were about late delivery of vehicles, persistently unsuccessful bidding for certificates of entitlement, and buyers being told to pay more for their cars after sales agreements had been signed.
The Consumers Association of Singapore (Case) has flagged a car parallel importer for questionable practices for the second time.
"Case offered SG Vehicles the opportunity to respond to the consumers' feedback," its spokesman said. "However, SG Vehicles failed to substantively respond by the stipulated time."
Other motor firms flagged recently by Case were De Auto Boutique, Exodus Global and Cars Today. All have shut down, with the boss of Cars Today - undischarged bankrupt Poh Chee Tiong - jailed last year for cheating 71 buyers, 14 sellers and four finance companies out of a total of $3.16 million in money and cars.
Car-related complaints continue to dominate Case's workload. Up to May this year, it received 1,024 complaints on this sector. The figures for last year, 2015 and 2014 were 2,916, 2,907 and 2,112 respectively.
The consumer association advises the public to negotiate for as low a deposit for cars as possible, and have delivery dates and the refund policy stated in the sales contract. Consumers are also advised to buy from CaseTrust-accredited firms (www.casetrust.org.sg).
"Consumers who wish to report any unfair practices committed can contact Case," its spokesman noted. "Or they may lodge a claim with the Small Claims Tribunal for losses or damages suffered as a result of any unfair practices."
The association said it is usually able to resolve about two-thirds of car-related cases filed with it. Case's hotline is 6100-0315.
The consumer association advises the public to negotiate for as low a deposit for cars as possible, and have delivery dates and the refund policy stated in the sales contract. Consumers are also advised to buy from CaseTrust-accredited firms.