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Over the weekend Toshiba announced that it had extended the scope of its recall, adding batteries supplied with Qosmio, Satellite Portege and Tecra models to the Dynabook units it had already begun replacing and bringing the total size of its recall to 830,000.

Fujitsu followed by confirming the recall of batteries supplied with 19 laptop models, though it declined to say how many were being replaced.

Meanwhile Dell added another 100,000 batteries to the 4.1 million it had previously recalled.

Add to that the figures from the Apple, IBM and Lenovo recalls and Sony finds itself having to foot the bill for the replacement of more than seven million batteries

The overheating occurs where small pieces of metal have been inadvertently deposited inside the batteries, causing them to short circuit. Sony said that it has since abandoned the process under which the faulty batteries were manufactured, and has also added new safeguards to its current process to reduce the chance of the fault recurring.

'It cannot be completely eliminated but we've taken steps to greatly reduce it,' said spokesman David Yang.

Although Sony has also supplied potentially faulty batteries for use in other electronics devices including portable DVD players and camcorders, there have been no reports of overheating, as these devices do not generate the amounts of heat that laptop processors, coupled with high-intensity usage, can produce.

The US Consumer Product Safety Commission said that it is working with Sony to identify whether any more batteries need to be recalled. It said that it was pressing the company to provide a comprehensive list as soon as possible in preference to the piecemeal recalls that have been announced until now.

Last week the Commission published a set of guidelines for laptop use - notably that they should not be used on your lap. It is also worth noting that manufacturers tend not to use the term laptop, preferring portable or notebook.