Media playback is unsupported on your device Media caption At least a quarter of the money assigned to the quake clean-up has been used on completely unrelated projects

Japan has spent funds intended for reconstruction after the 2011 earthquake and tsunami on unrelated projects, a government audit has found.

Projects financed by the $150bn (£93bn) fund include roads in Okinawa, an ad campaign for Japan's tallest building and support for whaling research.

Some 325,000 people remain displaced 18 months on from the disaster.

In some areas little reconstruction work has been carried out, reports say.

Analysis What is perhaps most surprising about this story to an outsider is the lack of fuss about it in Japan. It was barely reported by the Japanese media when the government audit was released last week. If such a damning government audit was published in the US or Britain one can imagine the howls from the media and opposition. The opposition leader here merely said it was "irresponsible". Most Japanese appear to be shrugging their shoulders. People here have learned from long experience to expect little from their political leaders, and they are rarely disappointed. For decades Japanese politics has been run on "pork" - the distribution of government money in return for political support. The misuse of tsunami funds fits that pattern. Of course that is of little consolation to people along the tsunami-devastated coast, still waiting for the reconstruction of their towns to begin.

Some 19,000 people were killed or remain missing following the tsunami and earthquake that struck north-east Japan in March 2011.

The government has passed a number of supplementary budgets to fund reconstruction efforts in affected areas.

But a government audit showed money had been used for unrelated projects reportedly included on the basis that they could boost national economic revival.

The findings come at a time when questions are being asked about the speed of Japan's reconstruction effort.

Takashi Kubota, deputy mayor of Rikuzentakata, a fishing port where nearly half of the houses were destroyed, told the Associated Press news agency that "not one single new building yet" had been built in the destroyed downtown area.

"In 19 months, there have basically been no major changes," he said.

Speaking in parliament on Monday, Japanese Prime Minister Yoshihiko Noda promised that problems would be addressed.

"There have been various criticisms made regarding how the budget for reconstruction has been spent," he said.

"We must listen sincerely to the voices calling for the utmost priority to be accorded to disaster area reconstruction. We will properly provide allowances for budget items that are truly needed by the disaster-affected areas and strictly narrow down other items."