A burgeoning middle class, as big as the population of France or West Germany, has emerged as a powerful social and economic force that holds promise of propelling India out of the ranks of the world's 15 poorest countries.

Although this new group numbers 70 million to 100 million, a small fraction of India's 750 million people, social scientist A.V. Pai Panandiker calls it the "emerging constituency" for Prime Minister Rajiv Gandhi.

Gandhi, for instance, shaped his budget to meet the demands of these new rich, who achieved wealth in the past five years from the vibrant successes of small industries that have sprung up around India's major urban centers of Bombay, New Delhi and Madras.

"They are the critical mass that now makes it feasible to raise the standard of the half of the people in India who live in poverty," said Mani Shankar Aiyer, a key aide to the prime minister.

But the political clout and free-spending ways of this new middle class have raised concerns that it is tearing apart India's social values, demanding more than its share of the fruits of the Indian economy, and further widening the gap between rich and poor in a country where the average per capita income is $260 a year.

"Those who do not share in the prosperity are only left with high costs," said Pran Chopra of the Center for Policy Research, and the spending of the new rich creates "stresses" for the 350 million Indians who live under an abysmally low poverty line.

The most visible sign of these new rich is their conspicuous consumption in a society in which spending on nonessentials has not been considered the ethical thing to do. "They are a new spending class in which the traditional Indian values of nonspending have never taken root," said Chopra.

Families of the new rich regularly crowd expensive restaurants reserved in the past for foreigners, special celebrations or those on expense accounts. This new class also has accelerated the growth of trendy fast-food restaurants, where pizzas and burgers cost as much as a full meal in a traditional Indian restaurant.

The new rich have even turned upside down the value that fat is beautiful. While being overweight formerly was seen as a sign of prosperity, a new interest in slimness has spawned health spas that advertise quick weight loss without diet or exercise.

Slimness, moreover, is now a virtue listed in marriage advertisements, along with expected earnings, educational achievement, a green card that allows residency in the United States and a generous dowry.

"A lot of people you wouldn't want your daughter to marry are sitting next to you at the best restaurants," said a high-ranking civil servant, a member of the top Hindu caste, the Brahmans.

"They have acquired an ethic that does not come from anything India or even Britain had. They no longer espouse the Gandhian values, traditional in this country even if we don't follow them," he continued, referring to Mohandas K. Gandhi, the ascetic spark behind India's independence movement. "They have learned to convert private vices into public values."

But not everyone in urban India feels comfortable with those values, and especially their effect on the young.

"Their children are swarming all over the place. It results in a tremendous confusion in the value systems that extends to their parents," said art historian Geeti Sen.

"I see it in my 16-year-old son wanting to go abroad on summer vacation. He says, 'Five of my friends are going. Why can't I?' My values are not to send him on a spree, but to go as I did when I went to college in America," she added.

Other parents complain that peer pressure forces them to buy high-priced brand-name athletic shoes for their children or allow them to go to discos in expensive hotels instead of the sandals and family-oriented entertainment of the past.

Children of the new rich are intensifying pressures to get into India's top-level schools, which already are tremendously competitive. Some parents complain of long interviews for nursery schools -- a phenomenon until now absent here.

In fact, many of the desires of what Pai Panandiker called the "assertive, vibrant and growing middle class of India" seem ordinary by American standards: telephones that work, a dependable supply of electricity, television sets, cars, air conditioners and video recorders.

But in an economy of scarcity such as India's, demands for these kinds of consumer goods place extraordinary stresses on the government's priorities for industrial development and expenditure of its foreign reserves.

The Indian government in 38 years since independence has eschewed consumer products in favor of producing and importing capital goods.

Rajiv Gandhi's mother, Indira Gandhi, built her constituency around India's poor, minorities and backward classes, said Pai Panandiker. But the new prime minister seems to have recognized the power of the new moneyed class.

"This is the consuming class in India, which has become a very powerful constituency, and they look toward Rajiv to take care of them," said Chopra.

"This is something of a lure Rajiv has to guard against. He has to guard against getting pulled into their complex of concerns" and ignoring other needs of the country.

These include fostering literacy in a country where more than 60 percent of the people neither read nor write, cutting a rate of infant mortality that ranks among the highest in the world, and improving life in India's 500,000 villages, half of which are not connected by roads and many of which have no sanitation facilities.

Gandhi's government rejects the notion that the prime minister has abandoned the needs of the poor in favor of the rising middle class. The prime minister has visited some of the poorest of India's rural poor, sometimes surprising bureaucrats with his insistence on going to inaccessible villages. In tribal areas of Madhya Pradesh State, for instance, he chastised local officials for their sudden effort to spruce up long neglected villages just before his visit.

"The poor in India determine changes in government," said Mani Shankar Aiyer, one of the prime minister's key aides.

"Rajiv just can't forget the poor. I don't think any of those 70 million or 100 million [of the new middle class] can forget the poor either. All we have to do is open the back door and see that the poor who live in the lanes outnumber us."

Gandhi, furthermore, sees the increasing numbers of middle-class Indians as the force that will allow the underprivileged to break out of their cycle of poverty.

"They make it possible to say we will enter the 21st century in the year 2000. That slogan took hold for the prime minister because it was seen as a real possibility," said Aiyer.

He added that the newly created wealth of an enlarged middle class is enabling the economy to grow at a geometric rate. "We've reached the critical mass" with these 70 million to 100 million people, he said.

Aiyer maintained that India's less privileged already are being carried upward on a tide of prosperity and now constitute the fastest rising class in the country. "There has been an explosion of the lower middle class," he said.

This group includes bicycle repairmen squatting by the side of the road, plasterers, electricians and carpenters.

"Today's middle class stretches all the way from industrialist to the meat seller," said writer Suneet Vir Singh.

Even landless farmers who are willing to move from their villages are now beginning to move upward as the demand for workers in factories has increased. Unskilled workers who once earned $1.25 a day now command a wage three times as great.

Still untouched are tens of millions of landless peasants, tied by custom and birth to their villages, and marginal farmers who remain in debt to village money lenders.

And the question remains among many Indians whether the emerging, free-spending and politically potent middle class cares about the poor.