World Bank President Robert S. McNamara proposed yesterday that former West German Chancellor Willy Brandt head a new private commission to help settle economic issues dividing rich and poor nations.

McNamara made the suggestion at the World Affairs Council in Boston, where he received the group's Christian A. Herter Memorial Award. A text of the speech was released by the World Bank in Washington.

He repeated his assessment given last October at the annual meetings of the bank and International Monetary Fund in Manila that an "impasse" had been reached at official levels on how to provide additional assistance to the poor nations.

Washington Post correspondent Michael Getler reported from Bonn that Brandt "is more positive than negative" on McNamra's proposal. If he accepts, a spokesman said, he would retain his role as a leader of the Social Democratic Party.

"The so-called North-South dialogue, bridging the gap between the rich and poor, clearly interests Brandt, and his left-of-center image around the world would undoubtedly make him a go-between of considerable stature, especially among less developed countries," Getler wrote.

Without increased aid, McNamara said neither the poorest of the poor nations (those with $100 or less per capita income) nor those in a so-called middle-income bracket (with per capita income over $200) can achieve satisfactory growth rates.

A private group headed by Brandt, McNamara said, could break the impasses by identifying "those political decisions which can command public and legislative support in rich and poor countries alike."

A Carter administration official, while agreeing that the dialogue between the rich and poor nations has been stalled for a year, was openly dubious about the McNamara proposal.

Carter aides dealing with international economic problems are committed to reopening the dialogue as an urgent priority but think it will take some months to formulate a complete approach and develop support on Capitol Hill, simultaneously working with other major nations.

"We're hoping they [the poor nations] won't rush us," said one incoming administration official. "So maybe this McNamara thing might buy a little time. Otherwise, I don't think it's worth much."

McNamara said in his speech that a private commission could provide no quick answer to the problems of developments, "for none exists." But he suggested that politically knowledgeable officials could make a contribution by focusing on fundamentals rather than details.

He said costs would be modest, and that he already had promises of financing participation from Minister Jan P. Pronk of the Netherlands and David Hopper, President of Canada's international development research center.

In New York, spokesman for U.N. Secretary General Kurt Waldheim said, "The secretary general expressed keen interest in this initiative, as he attaches the greatest importance and priority to ongoing process of deliberation and negotiation in various forums towards the establishment of the new international economic order."

The Herter award is given to an American citizen for fostering better international understanding. It went to Secretary of State Henry A. Kissinger in 1976.