Shares in Sony were knocked on Friday after the Japanese consumer electronics group was forced to recall thousands of defective laptops because of a risk that they could overheat and cause burns.

The recall affects 440,000 laptops in Sony’s Vaio TZ series that were sold across the world between May 2007 and July 2008. Sony has heard of 209 cases of laptops overheating, including seven in which users suffered minor burns.