New opinion polls show support for Japan's government has sunk to its lowest level since Prime Minister Naoto Kan came to power two years ago.

In surveys released Tuesday by NHK television and the Asahi newspaper, approval of the Democratic Party of Japan cabinet stood at about 15 percent, down from the low to mid-20s a month ago. About two-thirds of those surveyed said the prime minister should resign by the time parliament concludes its session next month.

Mr. Kan, who came to office last year, was already suffering from low approval ratings before an earthquake and tsunami struck the country in March. Public frustration over the government's response to the crisis and to the accident at the Fukushima Daichi nuclear plant have further eroded his popularity.

However other parties are not faring much better. The NHK poll found approval of the long-ruling Liberal Democratic Party stood at just 23 percent, while smaller parties polled in the single digits. Almost half the respondents said they do not support any party at all.

Mr. Kan has promised to step down shortly in the face of pressure from the opposition and members of his own party.

However he says he wants to remain in office long enough to ensure the passage of bills to finance earthquake reconstruction and promote renewable energy. The opposition has threatened to block the legislation until he resigns.