The Nuclear Regulation Authority (NRA) called in Tokyo Electric Power Co president Naomi Hirose and other executives over "the inappropriate management of contaminated water".
"The problems have been caused by a lack of basic checks," NRA secretary general Katsuhiko Ikeda told Hirose.
"I can't help but say that standards of on-site management are extremely low at Fukushima Daiichi," Ikeda said. He added the utility should strengthen its staffing levels, including by sending workers from other nuclear plants.
The meeting came as it was revealed that a key system to decontaminate radioactive water at the plant had stopped again.
Also Read
TEPCO said it halted the Advanced Liquid Processing System (ALPS) -- the only one of three that was in operation -- early today following "an alert suggesting abnormality in the process".
The firm said the cause of the problem was not known, but no leaks of radioactive water from the system had been detected.
ALPS is the great hope for TEPCO, which is struggling to cope with a huge -- and growing -- volume of liquid at the plant, where overheating reactors had to be cooled with thousands of tonnes of water after a tsunami hit in March 2011.
They continue to be doused, more than two-and-a-half years after the disaster.
Without a functioning ALPS, TEPCO is dependent on only one separate decontamination system to begin processing about 1,000 tanks full of water.
But neighbouring countries, global pressure groups and local fishermen are deeply opposed to the idea, unmoved by assurances that the radiation will be massively diluted as it mixes with the vast Pacific.