TOKYO -- Toyota Motor Corp. will boost its takeover defenses by increasing to more than 50 percent the stake its group firms hold in its major shareholder Toyota Industries Corp., the Asahi newspaper said on Wednesday.

The company aims to fix the share ownership structure of the group to block a possible attempt by a hostile bidder to take over Toyota Industries in order to gain access to the world's second-biggest automaker, the paper said.

Group companies, including Toyota Motor, Denso Corp. and Toyota Tsusho Corp., currently have about 45 percent of Toyota Industries. The automaker itself, which holds 23.5 percent of Toyota Industries, does not plan to raise its stake in the company, the paper said.

A Toyota spokeswoman said the company was studying various options, including poison pills, but no specific decision had been made.

Speculation has been rife that Toyota Industries, the 80-year-old textile-machinery maker from which Toyota Motor was spun off, could be targeted for a takeover as a cheap way to acquire a significant stake in the profitable automaker. Toyota Industries holds a 5.5 percent stake in Toyota Motor.

At Wednesday's closing share price of 2,835 yen, Toyota Industries' price-to-book ratio stands at around 0.8. Companies with ratios below 1.0 are generally considered prime targets for takeovers.

President Fujio Cho told Reuters recently that Toyota, along with its group companies, was considering various defense strategies but that it would take some time to reach a final decision.

The move comes as many Japanese companies set up plans to block unwanted takeover attempts following a series of takeover battles, including a high-profile one involving Fuji Television Network Inc., Nippon Broadcasting System Inc. and Livedoor Co.