Dell on Monday recalled the batteries in 4.1m of its notebook computers in what is believed to be the biggest safety recall involving the rechargeable power units.

The lithium ion batteries, made for the US computer company by Sony, were being withdrawn because they were liable to overheat and, in rare cases, produce smoke or catch fire, Dell said.

The product withdrawal comes at a time of heightened concerns about the potential dangers of laptop computers powered by unstable battery packs.

A number of cases of fires caused by laptops spontaneously bursting into flames have circulated on the internet, drawing concerns from aircraft regulators among others.

Roger Kay, analyst at Endpoint Technology Associates, said that while damaging to Dell at a time when the company is already under pressure, the recall should not have a lasting impact if the company acts quickly to replace the products.

The withdrawal comes at a sensitive time for the company, which has been fighting broader perceptions of poor customer service and slowing sales growth.

Mr Kay added, however, that it could have a deeper impact on Sony, given the Japanese company’s reputation for quality in the consumer electronics industry.

“Sony’s supposed to have a premium brand and they’re supposed to have control of their manufacturing,” he said.

The batteries covered by the recall were produced by Sony over the past two years. Dell has issued recalls of unstable laptop batteries before, but never on the scale of the current action.

The problems of overheating and possible fire have been caused by manufacturing deficiency that led to metallic impurities being introduced into some of the batteries, Mr Kay said.

The metallic parts intrude through the insulation that is supposed to keep apart the anode and cathode elements in the battery cells, leading to a spark that can cause a catastrophic fire.

Sony said on Tuesday that it expected to have to share the costs of the recall with Dell. Shares in the Japanese group closed slightly lower at Y5,210, in line with the broader Tokyo market.