The chairman of the American Stock Exchange and several corporate executives formed a new Washington lobbying group yesterday for "midsized businesses," called the American Business Council.

The council will be funded partially by the stock exchange and other corporations. Arthur Levitt Jr., the American Stock Exchange chairman, said he doesn't know the size of those contributions.

Neither the criteria for membership in the organization nor a definition of a midsized business has been determined, Levitt said. The group is interested in "growth firms" and those smaller than the Fortune 500 (the magazine's list of the largest industrial corporations according to sales), Levitt added, however.

Levitt said the heads of several midsized businesses last year expressed an interest in such a group to lobby on issues such as regulation, taxes, capital formation, inflation and international trade development.

The group hasn't set priorities for it's lobbying effort, but Levitt said he hopes the group can make its presence felt before the November elections.

A survey of 200 executives interested in forming the group showed that 64 percent of them believe midrange companies are underrepresented in forming national public policy, 76 percent feel disadvantaged by their lack of imput in national issues, 73 percent said an organization representing them would have impact and 58 percent said they are willing to participate in such a group.

Erenst J. Nagy, one of six members of the council's executive committee, said during a press conference yesterday that other business lobbying groups haven't adequately promoted medium-sized businesses or improved their relations with the public.

"I want to see the word 'profit' in this country not be a dirty word," Nagy said.