The operator of the crippled Fukushima nuclear plant will have no choice but to release more than 1 million tons of radioactive water into the Pacific Ocean, Japan’s environment minister said on Tuesday.

“The only option will be to drain it into the sea and dilute it”, Yoshiaki Harada said in a news briefing in Tokyo. “The whole of the government will discuss this, but I would like to offer my simple opinion.”

A government spokesman attempted to row back on the comments later in the day. "It is not true that we have decided on the disposal method," Chief Cabinet Minister Yoshihide Suga told reporters.

Three of the six reactors at the plant suffered melt-throughs after a magnitude-9 earthquake struck off the coast of north-east Japan in March 2011. The tremor caused a series of tsunami that knocked out the cooling system, leading to the second-worst nuclear disaster after Chernobyl.

Tokyo Electric Power Co (Tepco) has collected water used to keep the fuel cores from melting and groundwater that has seeped into the basement levels of the plant.

Tepco has claimed that the water only contains tritium, an isotope of hydrogen that is difficult to separate but poses little danger to human health. Government documents leaked to The Telegraph last year show that the water still contains radioactive material - including strontium, iodine, rhodium and cobalt - well above legally permitted levels.