TOKYO — A powerful and independent panel of specialists appointed by Japan’s Parliament is challenging the government’s account of the accident at a Fukushima Daiichi nuclear power plant, and will start its own investigation into the disaster — including an inquiry into how much the March earthquake may have damaged the plant’s reactors even before the tsunami.

The bipartisan panel with powers of subpoena is part of Japan’s efforts to investigate the nuclear calamity, which has displaced more than 100,000 people, rendered wide swaths of land unusable for decades and spurred public criticism that the government has been more interested in protecting vested industry interests than in discovering how three reactors were allowed to melt down and release huge amounts of radiation.

Several investigations — including inquiries by the plant operator, Tokyo Electric Power, and the government — have blamed the scale of the tsunami that struck Japan’s northeastern coast in March, knocking out vital cooling systems at the plant.

But critics in Japan and overseas have called for a fuller accounting of whether Tokyo Electric Power, or Tepco, sufficiently considered historically documented tsunami risks, and whether it could have done more to minimize the damage once waves hit the plant.