Those planning to sell their used cars on Carousell will be encouraged to send the vehicles for an evaluation first, following a collaboration between the online marketplace and the Consumers Association of Singapore (Case).

To make it convenient, sellers will soon be able to book appointments with authorised evaluators Vicom and the Automobile Association of Singapore using Carousell's app. The feature will be made available in about a month.

On average, there are 12,000 to 15,000 used-car listings on Carousell's app.

Case said yesterday that it is working with Carousell to protect consumers shopping for second-hand cars in the online marketplace.

It comes on the back of rising complaints about the car industry, which topped the consumer watchdog's complaints list for the sixth year in a row. Last year, Case received 2,335 car-related grouses, with 60 per cent involving a pre-owned car.

Case said it is also working with Carousell on a system which will identify pre-owned cars that have gone through a professional evaluation.

When launched, those found to be in a satisfactory condition will be identified in Carousell's listing with a Standard and Functional Evaluation (Safe) checklist mark. Even without the Safe mark, consumers can request repairs, a replacement, or a refund from sellers under Singapore's lemon law.

By pushing for a way to identify pre-owned cars that have been checked, Case hopes sellers will be encouraged to send their cars for an evaluation first, at a cost of between $100 and $200.

Consumers can also request sellers to do so.

Case said consumer complaints about defective cars have risen for three years in a row.

Last year, slightly more than half of all complaints about the industry related to defective cars, pre-owned and brand new. In 2013, it was 40 per cent.

Most complaints about the industry were about car defects, failure to honour contractual obligations, and misrepresentation of the cars sold, a Case spokesman said.

Said its education committee chairman, Mr Linus Ng: "Currently, it's not very instinctive for consumers to ask for an evaluation. We want to empower the consumers and encourage them to make a better-informed decision."

Case and Carousell are also looking at allowing sellers to upload a copy of the evaluation report on the online marketplace when they put their cars up for sale.

Case president Lim Biow Chuan reaffirmed the organisation's commitment to consumer protection and fair trading practices. "We will work together with our existing and new strategic partners to improve industry standards so that consumers are able to have peace of mind when shopping," he said.

Case will have a booth at the ST Classifieds biannual car event on April 7 and 8 to explain its initiatives.