A Japanese parliament probe into the nuclear disaster at Fukushima is expected to say the then prime minister fanned chaos in the opening days of the crisis when it publishes its final report Thursday.

The Diet's Fukushima Nuclear Accident Independent Investigation Commission will publish the dossier in the afternoon after having publicly interviewed top officials from the government and plant operator Tokyo Electric Power (TEPCO).

In interim statements, the commission has voiced criticism of Naoto Kan, who led the government when a 9.0-magnitude earthquake on March 11, 2011, sparked a deadly tsunami along the northern Pacific coast.

Giant waves crippled cooling equipment at the Fukushima Daiichi nuclear plant, triggering meltdowns that spewed radioactivity and forced tens of thousands of residents to flee.

The Kan government's initial response was slow and inadequate because it was unprepared, the commission has said in the past.

The body has also said Kan's aggressive but haphazard engagement with TEPCO after the accident did more harm than good.

"Frequent telephone calls were placed to the power plant from the prime minister's office and the government," the commission said in a statement issued last month.

"At times, very elementary questions were asked, forcing the work crew to direct their efforts to accommodate them," it said, adding that men at the site should have been left to tackle the crisis.

Kan came in for serious criticism for creating a distraction when he visited the Fukushima plant the day after the tsunami, as emergency workers scrambled to contain what would become full-blown meltdowns.

His administration was also lambasted for providing inadequate or confusing information to the public and was later found to have withheld computer models that showed how radiation from the busted reactors might spread.

There was deep distrust between the government and TEPCO, and engineers knew little about exactly what was happening inside the overheating reactors.

The dossier will be the third of its kind after a private group of scholars and journalists publicised their study February, followed by an internal report by TEPCO in June.

The Diet commission, launched in December at the demand of opposition parties, was designed as an alternative to the administration's investigation into the worst nuclear crisis in a generation.

The government's official Investigation Committee on the Accident at the Fukushima Nuclear Power Stations, launched under Kan in June 2011, will finish its report later this month.