Japan's efforts to clean up its nuclear disaster face intense global scrutiny ahead of the Tokyo Olympics, observers say, but despite government promises that Fukushima is "under control", the crisis will not be over by 2020. Speaking to Olympic chiefs in Buenos Aires just ahead of their weekend decision to award the 2020 Games to Tokyo, Japanese Prime Minister Shinzo Abe said there was nothing to worry about at the plant. Let me assure you, the situation is under control. It has never done and will never do any damage to Tokyo Japanese Prime Minister Shinzo Abe "Let me assure you, the situation is under control," he said in a speech lauded by Japanese media as key to Tokyo's success. "It has never done and will never do any damage to Tokyo. "Contaminated water has been contained in a 0.3 square-kilometre area of the harbour," he added in a question-and-answer session. "There have been no health problems and nor will there be. I will be taking responsibility for all the programmes with regard to the plant and the leaks." Critics at home and abroad say Abe's gloss on the 2011 disaster at Fukushima, where a tsunami swamped cooling systems and sent reactors into meltdown, is bordering on the dishonest. "I was flabbergasted by Abe's speech," said Hiroaki Koide, associate professor at Kyoto University Research Reactor Institute. "The problem of contaminated water is far from being solved. This problem has been going on all the time since the reactors were destroyed. Contaminated water has been leaking into the ocean ever since." On Monday, plant operator Tokyo Electric Power (Tepco) reported spiking levels of radiation in groundwater and said it was "likely" leaks from tanks storing highly polluted water had made their way into subterranean water that flows out into the sea. Tomoo Watanabe, director of the Research Centre for Fisheries Oceanography and Marine Ecosystems, said his understanding of the situation at Fukushima was not that it was "contained" in the way Abe explained it. But he said he agreed with Abe that it was necessary to look behind the alarming headlines to see the truth. "You may have a definite impression that the ocean is much more contaminated after Tepco admitted to the water leak, but we have not seen any signs of that pollution spreading to fish," he said. About 300 tonnes of mildly contaminated groundwater was entering the ocean every day, Tepco said. Watanabe said fish caught outside the harbour had shown a gradually decreasing level of caesium contamination, more markedly so in waters 20 kilometres from the plant. But, he added, pollution inside the harbour was high and fish living there should not be allowed to escape into the ocean where they would enter the food chain. After weeks of bad news, Japan's government stepped in last week with a US$500 million plan aimed at stemming the flow of polluted water. Hiroshi Miyano, a nuclear plant expert and visiting professor at Hosei University in Tokyo, said that despite the niceties in Buenos Aires, the clean-up was still a tall order. "The Olympic success may give positive momentum and speed up the road map, but I'm afraid it will still take at least two decades to decommission Fukushima at best."