A record quarterly loss at the world's largest pension fund is prompting a debate on whether its shift to stocks from bonds was excessive.

Domestic debt held by Japan's Government Pension Investment Fund returned 1 percent in the three months ended Dec. 31, while the nation's stocks erased 18 percent of their value, a GPIF statement showed on Feb. 1. The fund lost a record ¥14.8 trillion ($135 billion), or 9.1 percent.

While stocks helped the fund boost returns in the previous two fiscal years, the loss may provide ammunition for critics of Prime Minister Shinzo Abe, who backed a review of GPIF's strategy that led it to put about half of its assets in equities and cut domestic bonds in 2014.