The Japanese are planning for a welfare state of the future that will reinforce, not diminish, their country's devotion to the work ethic.

A new economic and social plan adopted by the Cabinet is a self- conscious effort to avoid laziness and low productivity that Japan sees as pitfalls of some Western countries, principally Great Britain -- at the same time that it encourages what is called a "Japanese-style welfare society."

It envisions more working years for older citizens, with pensions beginning later in life, and an annual unemployment rate of 1.7 percent. Limiting the work week to five days is encouraged, but it is the only concession to any concept of slower-paced living styles.

A government planner who had a hand in developing this guide for the future explained that it deliberately seeks to avoid what is widely described here as "the British sickness." The phrase is taken to mean low rates of productivity, incessant labor troubles and an indifference to hard work.

Japan's plan, he said, emphasizes the strong will to work, even among older citizens, and a high educational level that makes people adaptable to all kinds of work. Its philosophical underpinnings also assume muted class divisions, with high social mobility and a rough equality of opportunity.

"We think that these factors prevent a society like Britain's growing up in Japan," said Masataka Hirano, assistant director of the planning bureau of the Economic Planning Agency.

The plan is a mix of goals and guidelines for Japanese industry and government through 1985 and offers a glimpse into the way the Japanese see themselves at this stage. It assumes that the days of high growth and rapid economic development are finished and that Japan; having reached Western levels of personal income, should begin to chart a different course.

Its foremost target is a drastic improvement in social amentities and public services, which were overlooked in the economic boom days when Japan concentrated frenetically on private investment. One of the world's richest countries today, Japan is poor in the kind of public services other industrial countries take for granted. In terms of paved roads, sewerage, and park space, Japan ranks far below the United States and several European countries.

To close those gaps, the plan envisions spending more than $1 trillion on public works before 1985. That is 1 1/2 times the current rate of public works investment and means that by the end of 1985 what is called "social capital stock" will be doubled.

While much of the plan is a collection of informal and nonbinding guidelines, the commitment to public works spending is regarded as a firm government pledge to be reflected in annual budgets. An unusually high percentage of it -- more than 30 percent -- is to improve conditions directly related to daily life, such as schools, sanitation, housing, health and welfare.

Japan has been formulating such plans since the 1950s and has a generally good record of making them work. In the late 1950s and 1960s they were largely designed to fix economic growth targets and most were successful. Some targets were reached long before times set in the planning period ran out.

The new plan is unusual in stressing qualitative advances for human life over quantitative economic goals. Its language suggests a recognition that the pursuit of growth targets had sacrificed too many of the things that make life more comfortable and satisfying.

"There was a tendency in these times to lose sight of human relations at home and in the community," declares one section of the plan that attempts to describe a "new Japanese-style welfare society."

This has been a recurrent theme of the politics of the 1970s. Former prime minister Kakuei Tanaka formulated a grandiose design for restructuring the Japanese archipelago, but it was lost in the scandals that wrecked his administration.

The present incumbent, Masayoshi Ohira, talked much during his campaign last year of a return to family traditions and a more leisurely way of living. He advocated a system of "garden cities" that would revive communal satisfactions and neighborliness. The "garden cities concept" is mentioned in the new plan developed during his administration this year, but nothing specific is set forth to create the new communities.

The plan also represents Japan's first serious attempt to prepare for a rapidly aging population, a coming reality that many recognize as Japan's major social problem. Japan is facing the same againg problems that the United States and Europe are tackling. The difference is that it is happening here at a much faster pace.

The problem is a declining proportion of working-age people supporting a fast-growing proportion of elderly. Currently 8.6 workers support one person over 65 years of age. In just 40 years, the ratio will be only 3.3 to one. And the problem is made more acute here by the Japanese business community's tradition of forcing workers to retire in their mid-50s.

The plan proposes a two-directional solution that would start by raising social security expenditures and encouraging the old to work longer. By 1985 there would be a sizable increase in social insurance benefits, and the total social security burden as a percent of national income would rise from 9 to 11 percent.

The other part of the solution is typically Japanese: more work. It proposes that by 1985 the compulsory age of corporate retirement be extended to the age of 60 (it now varies from around 55 to 58) and urges that jobs be found for those over 60.