The bread spreads contained no trans fat, it was claimed.
But it seems that four of such products are not as healthy, after a spot check by the Consumers Association of Singapore (Case).
Flora Light 500G and Flora Original 500G were found to have 0.09g and 0.13g of trans fat per 100g respectively, while Sunny Meadow Spread with Canola Oil 500G and Sunny Meadow Spread with Olive Oil 500G, contained 0.12g and 0.19g of trans fat per 100g.
The nutritional information printed on the products indicated that there was zero gram of trans fat.
Case yesterday said it has shared the findings with the Agri-Food and Veterinary Authority of Singapore (AVA), which will now investigate the matter.
When contacted, AVA said it has conducted checks and will be taking enforcement action against the traders for inaccurate labelling.
The traders involved will also be required to rectify their labels.
The consumer watchdog's findings came from a survey by mystery shoppers of 20 common household margarine and vegetable oil-based spreads sold in Singapore. It was conducted in July last year to find out if these products' trans fat contents were within the 2 per cent limit imposed by the AVA.
Mystery shoppers can be people sent from companies or watchdog groups. They go undercover to purchase a product and service.
Case said the trans fat levels in all samples were within the statutory limit. However, some had a higher trans fat content than the amount declared on their food labels.
Mr Lim Biow Chuan, president of Case, said the differences between the declared values and the test results could be due to sample handling and the method used to analyse the sample.
Trans fat is a by-product produced in the industrial manufacturing of margarines and vegetable oil-based spreads.
Negative health effects associated with the consumption of trans fat include high cholesterol and the increased risk of developing Type 2 diabetes.
A FairPrice spokesman noted that the supermarket chain carries two of the products in question and is in contact with the supplier.
"FairPrice will reserve taking action pending further information and investigation by the authorities. However, prompt and firm actions will be taken on any of our suppliers if their products are found to be inaccurately labelled," she said.
A Cold Storage spokesman said it has taken note of the concern raised by Case and will continue to work to ensure that all its products are in compliance with regulations. The supermarket chain carries the Sunny Meadow spreads.