World Bank President Robert S. McNamara yesterday called for a major expansion of the institution's lending potential for the next 10 years to meet the rising demand for loans from poor countries and to take care of China, the Bank's newest and most populous member.

In an emotional address -- his last one -- to the annual joint meeting here of the World Bank and International Monetary Fund, McNamara said that with massive increases in the poor nations' oil bills and the certainty of continued inflation the Bank couldn't meet rising commitments over the next decade unless its authority to lend money is substantially boosted.

McNamara announced last summer that he will retire in mid-1981, when he reaches 65 years of age. He then will have served as president of the Bank for 13 years. A successor has not yet been chosen.

The World Bank president took the occasion to point an accusatory finger at the oil cartel for generating the current world economic crisis, saying that the poor nations could not continue to finance the deficits arising out of last year's 100 percent increase in oil prices.

He said that OPEC's price boosts had slowed economic growth in the Third World and thus made "their rate of social advance . . . substantially more difficult." Over the next five years, McNamara said the per capita growth gain in the less developed world would slump to 1.8 percent from the 2.7 percent level of the 1970s.

McNamara's proposal to enlarge the Bank is likely to prove controversial, considering the capital of the institution has just been doubled from about $45 billion to $85 billion. U.S. officials said privately that it may not have been prudent to raise the question of yet another increase in the Bank's size before Congress has approved appropriations for the U.S. share of the present capital increase.

But McNamara's argument is that inflation is eroding the real value of bank loans, just at the time the Bank proposes to expand loans for energy development to help meet balance-of-payments problems and to begin advancing substantial loans to the People's Republic of China.

Bank officials said that compared with loans of just under $12 billion this year, the tentative schedule calls for the Bank's commitments to rise to about $20 billion by 1985. In his speech, McNamara called for the kind of expansion that would run the total (in constant dollars) to $30 billion annually, of which $3.5 billion would be for China.

China's entry into the Bank (it also is a new member of the IMF) "has increased by 45 percent the number of people who now need, who now desire and who are now entitled to have World Bank Group lending," McNamara said.

President Carter yesterday pledged support, at least in principle, to an expanded World Bank. But no major nations have taken a stand on just how the expansion should be accomplished.

Some of the ideas floated by McNamara in his speech are bound to be controversial and almost certain to be opposed by some conservatives in the banking world.

A key question relates to McNamara's argument that the Bank ought to be permitted to make loans going beyond the total of its subscribed capital and reserves. When the Bank and IMF were created back in 1944, the Bank was limited to a one-for-one, or dollar-for-dollar ratio of its subscribed capital and reserves.

This is an extraordinarily conservative ratio and helps account for the Bank's AAA bond rating. Commercial banks, by way of contrast, normally make loans amounting to 15 to 20 times the capital and reserves they hold. Recently, the international commission headed by former German Chancellor Willy Brandt had recommended that the Bank could expand its loans and still maintain impeccable integrity by lending $2 for every $1 in the equity base.

McNamara mentioned no numbers in his speech but said that the old one-to-one ratio "is no longer really relevant to the Bank's financial condition or to the economic situation of its principal shareholders and that the result now is an unnecessary underutilization of the Bank's capital base."

An alternative way to finance the total package McNamara has in mind is to maintain the Bank's equity structure as it is and to create a brand-new affiliate with separate financing to make loans specifically for energy development in the Third World. As McNamara envisions it, this route would create a $25 billion agency, which would take over the Bank's existing commitments of about $13 billion for this purpose over the next decade and seek the balance of the $25 billion by borrowing from the Organization of Petroleum Exporting Countries and the rich industrial nations. That would free the Bank for nonenergy programs.

Many experts, including some high U.S. officials are concerned that some congressmen -- at this moment resisting voting for the U.S. share of the general capital increase -- will say: "Hey, wait a minute. All they have to do is to relax the Bank's capital base. They can lend on a two-for-one or three-for-one basis."

Aides close to McNamara said he realized the danger but felt that at this, his last speech to the world's financial elite, it was necessary to define what he conceived to be the Bank's urgent needs.