Old habits die hard among fishermen. Yoshio Ichida still rises for work every day at 3am and checks the engine of his five-ton boat. Then, as the sun rises over the Pacific and the trawler bobs gently in Soma wharf, he switches off the engine and gazes out at a sea too poisoned to fish.

Just 27 miles up the coast from this small harbour town, radioactivity from the Fukushima Daiichi nuclear power plant leaks into the ocean, and into the sardines, mackerel and squid that three generations of Mr Ichida’s family once caught.

Engineers are fighting what appears to be a losing battle to stop the leaks from worsening.

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Japan’s Nuclear Regulatory Authority (NRA) warned this week that the build-up of contaminated groundwater at the plant is on the verge of tipping out of control and that its operator, Tokyo Electric Power (Tepco), “lacked a sense of crisis” about the looming damage to the Pacific.

“Right now, we have an emergency,” said Shinji Kinjo, the head of an NRA task force. Mr Kinjo warned that leaking water had already flowed over a barrier built by engineers to block it. “The water could accelerate very quickly,” he said.

A survey released today by Japan’s Ministry of Economy, Trade and Industry said water laced with caesium and other radioactive materials is flowing into the ocean at a rate of 300 tons a day. The ministry, which oversees the nuclear industry, said it could not rule out the possibility that the water has been leaking into the Pacific since the crisis began more than two years ago.

Critics have accused the NRA of allowing Tepco off the hook. After months of denials, the embattled utility was finally forced to admit the groundwater leaks last week. Many suspect the admission was conveniently delayed until Japan’s pro-nuclear Prime Minister, Shinzo Abe, had solidified his power in the recent general election. Anti-nuclear voices in the media were muted during the election campaign and on occasion silenced completely: a YouTube video showing Mr Abe’s security confiscating an anti-nuclear sign during a speech in Fukushima has gone viral – but never been seen on TV.

Tepco said it is “unable to say” if the latest government figures for the size of the leak are accurate. But last week it admitted a cumulative leak of 20 trillion to 40 trillion becquerels of radioactive tritium since the earthquake and tsunami on 11 March 2011 that triggered the triple meltdown. Tritium, one of the cocktail of contaminants swimming in the onsite water, has a half-life of about 12 years.

This month, Tepco acknowledged that levels of radioactive caesium-134 were at their highest point since the disaster began. “We’re sorry for delaying this information,” said Yoshikazu Nagai, a Tepco spokesman. “We’re trying very hard to stop the leaks and fix the problem.”

Mr Ichida is not surprised. “Tepco is still trying to hide things from us,” he says. “They haven’t changed a bit. The 54-year-old, who survived the tsunami by driving his boat into the open sea, despairs that the crisis will ever end. “We must work to revive Fukushima fishing, but it is probably not likely,” he says, choking back tears. “Why would young people go into this profession?”

The build-up of contaminated water in the Daiichi’s ruined hulk was long predicted. Engineers pump about 400 tons of water a day onto the plant’s reactors to keep its melted nuclear fuel cool, and inevitably some leaks underground. The radioactive water is stored in more than 1,000 giant onsite tanks, which are almost full. The plant’s makeshift decontamination system cannot keep up with the amount of toxic water being produced.

The recent admissions have forced the government to step into what many experts now consider the world’s most complex ever nuclear clean-up. Mr Abe has ordered his government to help the struggling utility, a move that is likely to involve a huge injection of money into building an artificial underground wall to block the toxic water from reaching the Pacific. The Nikkei business newspaper estimates the cost of the operation at about $400m.

Experts say the government’s admission shows that the crisis at the Daiichi complex is being managed, not solved. “It is an emergency – has been since 11 March 2011 and will continue to be long into the future,” said Shaun Burnie, an independent nuclear consultant. He says onsite contaminated water contains three times the caesium released from the 1986 Chernobyl accident – the world’s worst nuclear disaster. “That underscores the scale of this never-ending threat.”

That news is a disaster to fishermen like Mr Ichida. Every Thursday he and his colleagues learn the latest radioactive readings from the sea. “Until recently, we only detected caesium, but now we detect strontium, which has a much longer life-span,” he says.

He and hundreds of other fishermen who used to work the Fukushima coast now while away their days mending nets and boats they may never use.

A government-funded project that pays them a little to collect debris from the sea ends in November. Some are contemplating virtually the only work left in the area: decontaminating Fukushima towns and villages poisoned by radiation.

“We have all made a living from the sea. We love the sea. We are proud of it and the work we got from it,” he says, choking back tears again.

“We must pass it on to the next generation. We will never get back what we had but we have to keep demanding that Tepco and the government take responsibility.”