A quarter of the £92bn budget for reconstruction after the tsunami and nuclear disaster in north-east Japan has been spent on unrelated projects, including a contact lens factory and whaling.

The findings of a government audit reinforce complaints over shortcomings and delays in the reconstruction effort. More than half the budget is yet to be﻿ distributed, stalled by indecision and bureaucracy, while nearly all of the 340,000 people evacuated from the disaster zone remain uncertain whether, when and how they will resettle.

Many of the non-reconstruction projects were included on the pretext they might contribute to Japan's economic revival, a strategy that the government now acknowledges was a mistake.

"It is true that the government has not done enough and has not done it adequately. We must listen to those who say the reconstruction should be the first priority," the Prime Minister, Yoshihiko Noda, told parliament. He vowed that unrelated projects will be "strictly wrung out" of the budget.

But ensuring that funds go to their intended purpose might require a change in the reconstruction spending law, which allows money to be used on "employment measures" and for other ambiguous purposes.