Experts investigating Japan's nuclear disaster said on Monday that the operator of the crippled plant continues to drag its feet in investigations and has tried to understate the true amount of damage at the complex.

The report, by a government-appointed panel, is the latest of several to fault Tokyo Electric Power Co and the government for doing too little to protect the Fukushima Daiichi plant from the massive earthquake and tsunami that set off three meltdowns there in the world's worst nuclear accident since Chernobyl.

The panel, of 10 independent experts in fields including radiation protection, medicine and law, also said the utility has yet to address problems within its own culture that contributed to its failings in the crisis - including employees "not fully trained to think for themselves".