Offshore tax havens have a new critic: small businesses.

On Tuesday, hundreds of these businesses will join in the announcement of a grass-roots campaign against tax avoidance that has already drawn support from a prominent lawmaker, The New York Times reported.

The campaign, Business and Investors Against Tax Haven Abuse, is backed by Senator Carl Levin, Democrat of Michigan, who in recent years has investigated offshore tax havens and the large companies and wealthy investors that use them.

Senator Levin plans to announce the campaign with its supporters, a coalition of three nonprofit groups — the American Sustainable Business Council, Business for Shared Prosperity and Wealth for the Common Good. They will release a 25-page report that contends that American multinational corporations use havens to avoid $37 billion in federal taxes each year, a figure the groups call conservative.

“This $37 billion could be used to fund initiatives to support America’s small businesses — the nation’s biggest job creators — by increasing their access to capital, increasing their opportunities to invest and rewarding entrepreneurship,” the report says.

With that money, the report says, “we could establish a $30 billion Small Business Lending Fund to provide capital investments to small community banks (those with less than $10 billion in assets) to increase lending to small enterprises.”

Bob Keener, a spokesman for a coalition member, Business for Shared Prosperity, said on Monday that 400 executives, investors and representatives of businesses had signed a petition in support of the campaign. They included a small shoe company in Maine, a consultancy in Virginia and cleaning services, he said.

The campaign is unusual because it is the first time that small businesses have organized to combat offshore tax avoidance and evasion in a significant way.

“The Business and Investors Against Tax Haven Abuse campaign represents the first time in recent years that business people who believe tax havens are bad for business are mobilizing publicly to end the abuse,” Mr. Levin said Monday in a statement.

The Treasury Department estimated in 2009 that the international gap between taxes owed and taxes paid ranged from $43 billion to $123 billion a year for corporations and individuals.

The report calls for laws that would block transfers of intellectual property intended to evade taxes; ban shell corporations that earn profits offshore, even when a corporation’s management team is based in the United States; repeal a rule that allows American corporations to reduce or eliminate their United States tax bills if 80 percent of their business takes place overseas; and set penalties for government contractors that use tax havens.