Firms including Yahoo Japan Corp., bookstore chain Kinokuniya Co. and online game software developer Dwango Co. are urging the government to levy the sales tax on e-books and music downloaded from overseas websites to bring them in line with domestic online sales.

Under the current tax system, only products from sellers within Japan and imported merchandise are subject to sales tax. E-books and other digital content distributed by online retailers such as Amazon.com Inc. are exempt from sales tax.

"Japanese companies are at a disadvantage from the standpoint of price competitiveness," the group of 13 companies said in a statement Wednesday.

The Liberal Democratic Party-New Komeito ruling bloc has been weighing imposing sales tax on overseas firms engaged in online distribution in Japan since last year, but did not reach a conclusion on the matter in the tax revision for fiscal 2013.