WASHINGTON – Reports of elaborate schemes by charities and nonprofit organizations to avoid paying taxes have senators redoubling calls for stronger regulation of the charitable sector.

In one example, drawing the outrage of lawmakers at a Senate Finance Committee hearing, wealthy big-game hunters have reportedly been offsetting the costs of their safaris by donating mounted heads of exotic animals to a Nebraska museum and claiming tax deductions as large as $10,000, or 10 times the market value of the trophies.

Holding the stuffed head of a Spring Bok, a kind of antelope from South Africa, the committee’s chairman, Senator Grassley, a Republican of Iowa, declared that such abuses must stop.

“This type of scam gives new meaning of the term tax ‘game,'” said Mr. Grassley of the scheme, which was first reported yesterday in the Washington Post.

The taxidermy problem is “just one example” of “pie in the sky” valuations of gifts to charity, he said.

The committee also heard testimony about mismanagement and profiteering by managers of tax-exempt private foundations. In one case, a foundation created to improve education in Tennessee was paying its director several millions of dollars in compensation, and paying for her purchase of two minor league hockey teams in Mississippi.

Senators also heard of a tax-exempt hospital charity in Minnesota that paid for more than 30 trips to Hawaii for its employees, a trip to Grand Cayman Island for its president and his wife, and $5,000 dinners. It also sent executives on a three-day wine tour of Napa Valley in private limousines and hot-air balloons, as part of a trip designed to help them find their “moral center.”

And repeatedly, the committee has heard of donors vastly inflating the value of the used clothing, household items, land easements, and closely held stock that they donate to charity in order to secure large tax deductions.

“We are now at an important juncture,” the commissioner of the Internal Revenue Service, Mark Everson, told the panel. “The twin cancers of technical manipulation and outright abuse that we saw develop in the profit-making segments of the economy are now spreading to pockets of the nonprofit sector,” he said.

The IRS has increased its budget for investigating tax-exempt organizations by 20%, said Mr. Everson, who urged Congress to approve President Bush’s 2006 budget request for an additional $14.5 million to increase enforcement in the sector. Mr. Everson called for stricter penalties for tax evaders, mandatory electronic filing for all nonprofit tax returns, and the ability to share information with state regulators who also investigate tax abuses.

Mr. Grassley said he hopes to “move quickly” on legislation that would impose stricter governance standards on charities and curtail tax evasion that has prevented the government from collecting more than $300 billion in annual revenues.

“Congress must revisit the laws in this area to make sure that it’s charity that benefits from the laws rather than private interests,” Mr. Grassley said.

The committee is considering a wide range of options, from salary limits for nonprofit officials to stricter governance and audit requirements. Lawmakers are also considering caps on certain charitable tax deductions, such as a $500 limit on used clothing and an end to tax deductions for donations of property that is still used as a personal residence.

From his recently acquired seat on the powerful Senate Finance Committee, Senator Schumer yesterday signaled that he plans to be an outspoken ally of New York City’s charities and nonprofit organizations.

Mr. Schumer cautioned the committee to avoid “one-size-fits-all” rules that would burden the small organizations that account for the vast majority of charities in New York, and he warned senators that new restrictions on tax deductions would discourage giving.

Echoing arguments of nonprofit groups, Mr. Schumer said the federal government should focus on redoubling enforcement of existing laws rather than imposing additional regulations on nonprofits, which he said are crucial to delivering social services to many New Yorkers.

“My constituents tell me that many reforms sought by the committee could be accomplished with greater enforcement of the laws on the books,” Mr. Schumer said.

The senator also doubted the wisdom of suggestions to cap the compensation for executives, staff, board members, and trustees at private foundations.

Instead, he suggested excluding compensation from the foundations’ obligation to pay out 5% of their assets each year.

While charities and nonprofits play an important role in all states, Mr. Schumer said, “They are an integral part of the fabric that makes New York a great and special place.”

The New York metropolitan area has the “largest concentration of philanthropic capital in the world,” said Mr. Schumer.

There are 27,000 nonprofits in the city that employ 528,000 people on a $22 billion payroll, according to the New York Community Trust.

Most of the nonprofits are “very small,” Mr. Schumer said, and 98% have revenues under $5 million.

The senator was particularly concerned about a proposal to reduce the tax deduction for donations of stock that is not publicly traded.

Many successful entrepreneurs “have stocks and not much else” to give away, he said. “The anecdotal information I’ve received from my constituents is that such a change would be devastating.”

However, a senior specialist in economic policy at the Congressional Research Service, Jane Gravelle, testified that academic studies suggest such rule changes would not reduce the amount of charitable giving, but rather cause more donations to be made in cash.

Nonetheless, Mr. Schumer’s concerns were shared by Senator Santorum, a Republican of Pennsylvania, who said many of the proposals under consideration by the committee would make charities and donors “bear a significant burden for dubious public benefit.”

The president and CEO of Independent Sector, a national coalition of charities, foundations, and corporate philanthropy programs, Diana Aviv, told the panel that ending abuse will require a combination of government oversight and self-regulation.

The group is developing its own proposals that include stiffer penalties for financial abuses by directors and mandatory audits for the largest organizations. But she warned senators against imposing rules that will discourage giving and “throw out the baby with the bathwater.”