The government on Wednesday warned Sharp Corp. that one of the company's ads has violated a law by overstating the performance of its vacuum cleaner.

The ad claims Sharp's Plasmacluster unit built into the vacuum cleaner breaks down dead mites and their droppings into nonallergic substances by releasing ions.

But the Consumer Affairs Agency said its tests conducted on the vacuum cleaner show the ad, which was run by the electronics maker between October 2010 and this April, exaggerated its capabilities.

The agency asked Sharp, currently struggling amid poor business results, to prevent recurrences of such overstatements. The company has generated sales of about ¥23.4 billion during the period in which the ad was run.

A number of Sharp's other products also feature its signature Plasmacluster ion technology. A public relations official for Sharp said it can't comment at present because the company is still studying the written order sent by the agency.

In a related development, Toshiba Home Appliances Corp. on Tuesday offered to replace 73,847 vacuum cleaners sold domestically after three of the appliances either caught fire or emitted smoke between April and September.

The products in question were made in China between October 2009 and March 2011, and nonflameproof materials were mistakenly used for exhaust gas filters, Toshiba Home Appliances said.