“It’s quite alarming based on the results,” Professor Michael Hui King-man, chairman of the council’s publicity and community relations committee, said.

“The good news is that the three samples with the most serious problems ... they have voluntarily removed their products from shelves.”

The recalled models were produced by Philips and PMS.

The council found six models had inadequate construction. Seven units failed construction quality standards after being put through an endurance test of plugging and unplugging a socket 15,000 times.

All models tested came with power switches for each socket, 10 of which failed to meet standard requirements. The plastic cover of one of the switches melted after completing a temperature test.

The Electrical and Mechanical Services Department told the council that if extension units that were not recalled are used under “normal” conditions, they should not pose a safety risk.

Hui said he hoped the department would step-up efforts to conduct more checks.

“To ensure public safety, EMSD will step up shop inspections of extension units and remind the trade to ensure that their products are manufactured and tested in strict compliance with relevant international standards,” a spokesman for EMSD said.

Consumer Council chief executive Gilly Wong Fung-han said that while the council and EMSD were doing their job conducting safety checks, the responsibility was with the manufacturers.

“They are responsible to provide safe and proper products for use by consumers,” she said.

Hui added that consumers should be aware not to use heavy power-consuming products with power extension units, such as heaters and air conditioners.

A Philips representative said the recalled extension cord had been certified by an accredited lab, and believed the unit tested by the council was “an isolated workmanship issue”.

The electronics giant will “review and further tighten process control guidelines for future products,” the representative added.