Higher education officials yesterday sharply criticized a Department of Education study that shows private colleges spend significantly more than public institutions to educate students, saying the report was technically flawed and politically motivated.

College representatives said the study is an attempt by Education Secretary William J. Bennett to bolster his arguments that colleges waste money and, as a result, federal financial aid should be scaled back.

But department officials stood behind their study, which reported that the average cost for a private institution to supply a bachelor's degree was about $28,400 in 1983, compared to $18,500 at public institutions. They countered that the report had no political aim and that education officials were "paranoid" and attempting to censor the study.

"This is a fundamentally bad study," said Richard Rosser, president of the National Association of Independent Colleges and Universities, which handed out a pre-publication version of the report at a news conference. "It's just one more example of what has got to be a blatant attack against independent colleges and universities in this country."

Assistant Education Secretary Chester E. Finn Jr. responded: "It's sad that the higher education community, instead of welcoming the information . . . has trashed a scholarly report before it's even been published . . . . On their part it's paranoid."

The intensity of the exchange reflects the deteriorating relationship between the department and many of those in higher education, who see Bennett as adversarial and overly ideological. Federal officials blame the rift on a defensiveness among college administrators, particularly on the subject of tuition and college costs.

The topic has been high on the public agenda recently, with release of a College Board study Aug. 7 showing that college tuitions will rise 5 to 8 percent this year and the cost of a four-year education at some private institutions could reach $75,000.

The Department of Education study, "Estimating the Cost of a Bachelor's Degree," reported that "on average, degrees from private institutions were 54 percent more expensive than those from public institutions . . . these institutions spent more money on instruction in 1983. The curious question is: How can these institutions keep their full costs down while they are spending enormous amounts of money on instruction?"

Robert Zemsky, chief planning officer at the University of Pennsylvania and one of four academics asked by the department to review the study, said the report reaches the wrong conclusion in part because it counts financial aid as an expense, a calculation that inflates the costs disproportionately for private schools.

Other college representatives said expenses at public institutions were underrepresented because many costs, including employe benefits and utilities, are often calculated as state rather than institutional expenses.

Frank Balz, executive director of the National Institute of Independent Colleges and Universities, said a study conducted in the state of Washington is more accurate because it compared public and private institutions that were similar in type and size, finding roughly comparable costs at comparable institutions. That study found that in 1986 costs were $9,173 per student at the public research universities in the state, $8,047 at four-year public institutions and $8,340 at independent colleges.

Studies conducted by other states correspond with the Washington study, Rosser said.

The author of the new study, department researcher Duc-Le To, acknowledged that the only available data for his study may be inadequate, but defended his methodology. In a written response to criticism by academic reviewers, he said the report was "only intended to stimulate discussion and research on the subject, and to some degree, that goal appears to have been achieved."