TEPCO has previously been criticized for numerous delays in releasing information and in responding to problems at the damaged plant.
TEPCO acknowledged in July that contaminated underground water has been flowing into the Pacific Ocean since soon after a massive earthquake and tsunami hit the plant in 2001, knocking out its power and cooling systems and causing three reactors to melt.
Recent leaks of radioactive water from storage tanks have added to fears that TEPCO is unable to cope with the large amounts of contaminated water generated by the process of cooling the nuclear fuel in the damaged reactors.
Tanaka said TEPCO improperly described the radioactivity of "hot spots" recently found near water storage tanks using a unit that measures potential human exposure levels instead of one that measures the level of radioactivity of the water itself.
"Nobody in the world does that," he said. "It's scientifically nonsense."
He said TEPCO often seems to release unconfirmed information to avoid being accused of covering up.
More than 1,000 tanks have been hastily built at the plant to store more than 335,000 tons of partially treated radioactive water. The amount of radioactive water grows by 400 tons daily.