A Justice Ministry panel on Monday began reviewing what critics call Japan's lax criminal penalties against rapists and other sex offenders, in the nation's first comprehensive effort in more than a century to overhaul laws on sex crimes.

The panel of outside legal experts is tasked with discussing ways to revamp sex offense statutes that have remained untouched since their enactment in the Meiji Era, save a few minor changes.

During the first session of its deliberations Monday, the panel discussed whether to make sex crimes such as rape and indecent assault prosecutable without a complaint being filed by a victim, the Justice Ministry said.