The Consumer Council said on Thursday that over 90 percent of margarine and spreads it has examined contain substances that can cause cancer.

Out of 16 samples of margarine and spreads containing vegetable oil, 15 were found to have genotoxic carcinogen glycidol, with one – Earth Balance Original Buttery Spread – exceeding the EU's maximum permitted level.

Over 80 percent were also found to contain 3-MCPD, which at excessive levels can harm health, including a person's kidney functions.

The watchdog said samples of butter were not found to have such substances, but had a relatively higher fat content.

Among 12 samples of butter tested, one of them – Crisco All-Vegetable Shortening – contained over 99.9g of fat in each 100g.

Gilly Wong, chief executive of the council, said people should weigh up the pros and cons of butter, margarine and spreads.

"Butter doesn't contain pollutants or carcinogenic toxic substances, but it is high in saturated fat and trans fat. For margarine and spreads, they contain pollutants and carcinogenic toxic substances of different levels, but their monounsaturated fat and polyunsaturated fat is much higher than natural butter, which can help your body," she said.

She reminded people to control their consumption levels and select products carefully to safeguard their health.