Environmental groups that frequently spar with the Bush administration over protecting the air, water and human health also have collected millions of dollars in government grants, failing in one recent case to properly account for the money.

More than 2,200 nonprofit groups have received grants from the Environmental Protection Agency over the last decade, including those that lobby and sometimes sue the agency.

One of the most prominent, the Natural Resources Defense Council, was cited in a recent audit for failing to properly document more than a third of the $3.3 million it received in three EPA grants.

NRDC used the money to conduct research and education on storm water pollution, and to develop and encourage energy-efficient technology, according to EPA's inspector general, the agency's internal watchdog.

NRDC acknowledges recordkeeping errors dealing with benefits, timesheets and indirect costs. It cited in part erroneous direction from EPA itself about what was required.

"We're not running away from that and that's why we've offered to pay back the money," amounting to some $75,000 once the documentation was corrected, said NRDC attorney Mitch Bernard. He noted there was no criticism of NRDC's research. The case is not yet finalized.

Groups like NRDC, with their stables of scientists and extensive monitoring of environmental policy, often are seen as barometers that help shape opinion on key issues.

Asked about potential conflicts between their government watchdog role and their financial connections to EPA, the groups say that grants for specific technical, research and education projects don't interfere with their advocacy, which they conduct with separate funds.

"It may be confusing to the public that with the right hand we're accepting government money and with the left hand sometimes we're beating up the government," said Charles Miller, communications director for Environmental Defense, which has received more than $1.8 million from EPA since 1995.

"But the government is a complicated beast. Some of the things they're doing we think are wrong. A lot of the things they're doing we think are right. We're using the grant money to further the environmental cause," Miller said.

Others see such grants posing at least an appearance problem.

"It raises the specter of a conflict of interest. It's an ethical question," said Roberta Baskin, executive director for the nonprofit Center for Public Integrity, an investigative organization that accepts no government, union or corporate money. "They're supposed to be watchdogs. Does it make you a lap dog if they're funding you? Is your loyalty to -- the environment --or is it to the bottom line?"

From another standpoint, the grants have drawn fire in recent years from political conservatives, like Sen. James Inhofe, R-Okla., chairman of the Environment and Public Works Committee, who last year called environmental groups "simply Democrat political machines."

EPA doesn't turn away grantees because of their criticism or lawsuits, said spokesman Bob Zachariasiewicz. A new policy requires competitive bidding for any grant over $15,000 and the money cannot be spent on lobbying, political or litigation work.

NRDC spokesman Jon Coifman said there's been no dilemma for his $65 million a year organization whose government grants were less than 1 percent of its budget --"far too small to have any effect one way or the other on NRDC's broader policy decisions," he said.

NRDC has sued EPA 35 times the past two years, he said. "We don't feel that we've given up an inch of our integrity on this," Coifman said.

Other recipients made the same point but acknowledged potential perception problems.

"It's a legitimate question," said Ben McNitt, spokesman for the National Wildlife Federation, recipient of $292,620 from EPA. He said government grants in 2004 were less than 1 percent of NWF's annual revenues, and the group's lawsuits and vigorous criticism of EPA policies on wetlands, mercury emissions and other issues prove it is not co-opted.

The Pesticide Action Network, which advocates for reduced pesticide use, received a $97,000 grant to develop online information on pesticide use and water pollution, co-director Steve Scholl-Buckwald said.

"In every case we're asking the question: Is this money allowing us to do something we want to do and it or is it something someone else wants us to do?"

EPA conducts about half of its work, or $4.3 billion in 2004, through grants, mostly to state, local and tribal governments. Non-profits account for about 7 percent of the total, including many ordered by Congress. Besides the environmental groups, many recipients are agriculture and industry allies with keen interest in EPA regulatory policies, along with academic, civic and other groups that advocate on health, the elderly and consumer issues.

Overall, the inspector general has cited grant oversight as an EPA weakness. In a September report, it said EPA has improved but still needs to pursue greater accountability from project managers. Zachariasiewicz said that process is ongoing through new performance measurements.