As global investors await Prime Minister Shinzo Abe's third arrow of economic growth policies -- a package of corporate-friendly regulatory reforms -- his government is quietly moving forward with a measure irking the business community: a bill aimed at encouraging more consumer class-action lawsuits.

The cabinet approved the measure in April, and aims to have it pass parliament before the session ends in June. Specifically, the law would for the first time allow a class of Japanese consumers to collect as a group monetary...