Consumers were unhappy about the chips used in the laptop model

The group has been sued over charges its laptops contained a different, cheaper chip than those advertised.

According to state media reports at least 20 lawsuits have been filed against the Texas-based firm.

In a statement on its Direct2Dell website, Dell admitted it had made an "unfortunate and unintended marketing mistake" and apologised for the error.

Dell said it had contacted customers and explained the difference between the two chips and offered full refunds to any customers who were still unsatisfied.

Update delays

Spokeswoman Sharon Zhang said the error took place after the firm began to switch the chips used in certain laptop models, but sales brochures and order forms were not updated in time.

The problems centre on Dell's Inspiron 640M laptop. According to marketing materials the model was fitted with Intel's T2300 chip, which includes a system dubbed "Vanderpool" which makes a computer more capable of running multiple operating systems at the same time.

However, in China, and some other countries, Dell instead fitted the laptops with the T2300E chip, which lacked Vanderpool. The chip also costs $32 less than the T2300.

A report in the China Daily newspaper said the first case accusing Dell of false advertising had been filed in Shanghai on 26 July, and a further 19 were filed on 8 August in Xiamen.