TOKYO — When threatened by soaring oil prices in the 1970s, Japan's response was swift, smart and successful.

TOKYO — When threatened by soaring oil prices in the 1970s, Japan's response was swift, smart and successful.

It transformed itself into the most efficient user of energy in the developed world, thanks to government leadership, engineering skill and a public that embraced conservation.

Now Japan faces a much more fundamental threat to its future — demographic decline that experts say will delete 70 percent of its work force by 2050.

Yet the all-hands-on-deck response that quelled the oil shock is conspicuously missing from Japan's policies for a disappearing population.

"Unfortunately, the people do not share a sense of crisis," said Masakazu Toyoda, a vice minister at the Ministry of Economy, Trade and Industry. "Yes, we deserve some kind of criticism."

Inside the government, there is growing agreement that Japan can head off disastrous population decline by significantly increasing immigration.

Japan has the world's highest proportion of people older than 65 and the world's smallest proportion of children younger than 15. Without immigration in substantial numbers, it will soon run perilously low on people of working age.

Yet among highly developed countries, Japan has always ranked near the bottom in the percentage of foreign-born residents. In the United States, about 12 percent are foreign-born; in Japan, just 1.6 percent. Most immigrants here are from Asia or South America. The largest number come from Korea (about 600,000 people), followed by China and Brazil. The Brazilians are mostly of mixed Japanese descent.

Yet there is little or no political will here to persuade or prepare the public to accept a sizable influx of foreigners.

Based on a round of interviews with Prime Minister Yasuo Fukuda and several other senior government officials and politicians, the issue is too politically toxic for extensive public discussion.

"We need to work out policy in order to actively accept increasing numbers of immigrants," Fukuda said, adding that his advisers are researching and discussing the issue.

But as soon he explained the need for immigrants, Fukuda, whose approval ratings are an anemic 24 percent, said he had to remain cautious on the issue.

"There are people who say that if we accept more immigrants, crime will increase," Fukuda said. "Any sudden increase in immigrants causing social chaos (and) social unrest is a result that we must avoid by all means."

In his speeches and public appearances, Fukuda rarely mentions immigration. In that respect, he is like most politicians in Japan, which has little historical experience of substantial immigration.

"We really need to let the people know that the economy simply cannot be managed without the help of foreigners," said Seiji Maehara, a member of parliament and a vice president in the opposition Democratic Party of Japan.

But Maehara said no leading politician here has the courage to say as much to voters. The silence is enforced, in part, by political ambition.

The Democratic Party, which last year won control of the upper house of parliament, has a rare opportunity to take control of the government away from the Liberal Democratic Party, which has more or less run Japan since the 1950s.

The ruling party, with the unpopular Fukuda as its leader, is more vulnerable to defeat than it has been in decades, according to many analysts. An election is possible this year but will probably be held in the fall of 2009.

Until then, as politicians from both parties jockey for advantage, Maehara said it is virtually certain that the "urgent matter" of immigration will get no public hearing whatsoever.

There is another way for Japan to slow population decline and maintain its workforce: persuade more Japanese women to marry, have children and remain on the job.

Japan is failing badly in this area. The percentage of women who choose to stay single has doubled in the past two decades. When they do marry and have children, they drop out of the workforce at far higher rates than in other wealthy countries.

These worrying numbers have been bouncing around inside government ministries for several years. But the policy response — in a government dominated by men in their 50s, 60s and 70s — has often been tentative and sometimes insulting to women.

A health minister last year described women of childbearing age as "birth-giving machines" and instructed them to do "their best per head" to produce babies.

In recent months, however, the government's tone has changed substantially, as powerful politicians and business leaders have begun to call for enlightened government intervention that would ease the cost and complications of raising children.

"We need to organize our society so that women and families will be able to raise children while working," Fukuda said in the interview.

To that end, the government is working on a bill to require companies to offer shorter hours to parents with young children and to stop requiring them to work overtime.

Still, Fukuda's government is not proposing a major new increase in spending on national child care, in part because it does not have the money.

Japan struggles to pay the pension and health-care costs of the world's oldest population. It also has a debt burden that amounts to 180 percent of its gross domestic product, which is the highest ever recorded by a developed country.

Government spending on child care here amounts to a quarter of what is spent in France and Sweden, where comprehensive family policies have increased the birthrate and kept women at work.

"I think we still lack adequate efforts on that front," Fukuda said.