Former World Bank president Robert S. McNamara and his French and Japanese colleagues today sharply criticized proposals for consolidation of Third World debts into long-term loans at lower interest rates.

In a report to the Trilateral Commission, McNamara; Takeshi Watanabe, a former senior Japanese diplomat; and French economics professor Jacques Lesourne argued that the seriousness of the debt crisis has been overstated.

What the report rejected were dramatic proposals that have been made in Congress and some academic circles calling for the World Bank or some other official institution to take over the Third World debt at a discount and turn at least some of it into longer-term loans at lower interest rates. Proposals along these lines have been made by Sen. Bill Bradley (D-N.J.), Rep. Charles Schumer (D-N.Y.), New York banker Felix Rohatyn, and Princeton University Professor Peter Kenen.

An official summary of the report released here approvingly quoted the view of Jacques de Larosiere, managing director of the International Monetary Fund, that "there does not exist a global debt crisis." The authors agreed with de Larosiere's contention that the debt problem is one of liquidity--a temporary but embarrassing shortage of cash resources--rather than one of insolvency.

They urged in their report that the borrowing countries--who now owe a total of nearly $600 billion--undertake austerity reforms at home and that the commercial banks and international lending institutions continue "to increase their net credit outstanding at appropriate rates."

The Trilateral Commission is a group of nearly 300 private business executives, bankers and others from Japan, North America and Europe who meet annually to discuss the mutual problems of economics and security among these countries.

Although the McNamara report generally was praised, it also ran into criticism in the privacy of the Trilateral Commission meeting. Many argued that the report was too complacent and needed to go beyond its recommendations for dealing with the present crisis.

Some members argued that, even if the current problem is ameliorated, another debt crisis would spring up within a year's time unless additional funds are found that will allow borrowing countries not only to maintain their interest payment schedule, but to maintain their level of imports from the rich world.

The McNamara report said "there is a general misconception that the current financial crisis reflects mismanagement by developing countries and greediness by commercial banks."

Although it acknowledged that there had been some such isolated cases, the authors contended that the great majority of Third World borrowers remain creditworthy and that both the bankers and the borrowers had performed well.

The report said that, if there had been a policy failure, it was by major countries that had pursued policies leading to excessively high interest rates, and those countries that had not provided adequate incentives for higher agricultural output in the Developing World.

The thrust of the private criticism from the floor of the Trilateral Commission session was that, regardless of de Larosiere's conclusion, the debt crisis easily could be transformed from a liquidity problem into an insolvency problem.

One critic assailed the report in a detailed assessment as reflecting only conventional wisdom about a loosely structured banking system that actually had begun to destroy itself. He warned that, unless the resources for the IMF, the World Bank and other lending organizations were vastly increased, the world would be headed for a major financial crisis.

But the McNamara report did not advocate an absolute standstill. It recommended:

Allowing the IMF to supplement its resources by borrowing directly from the market.

Relaxing the present IMF borrowing limit of 450 percent of a member's quota. (This is opposed by the United States).

Increasing the role of the World Bank and Bank for International Settlements, both of which should be more active in the Paris Club rescheduling operation.

Although it did not endorse proposals being considered by Congress to toughen regulatory procedures for international lending, the report urged that the IMF and World Bank share more information with the commercial banks on a "candid and active basis" to help the banks understand better the real economic situation in the countries to which they make loans.

On development aid issues, the report was sharply critical of the American shortfall in aid to the World Bank's soft-loan agency, the International Development Agency, and said bluntly that the IDA "is now bankrupt because of the failure of the United States to honor its commitments."