A routine update of the formula the federal government uses to calculate a student's need for aid apparently will shift more of the financial burden of college onto students. One group of financial analysts predicts that the change, first reported in The New York Times on Friday, will force undergraduates to spend at least $10-billion more on higher education in 2004.

The Times reported that the change, to update the tax data used in the formula, would reduce the government's contribution to higher education by hundreds of millions of dollars, and lawmakers were swift to respond. Sen. Edward M. Kennedy, Democrat of Massachusetts, said he would introduce a bill this week to block the use of the tax data, pending an investigation by the General Accounting Office, the investigative arm of Congress. Sen. Kennedy's office said he has the support of 30 senators.

Rep. George Miller of California, the senior Democrat on the House Committee on Education and the Workforce, sent a letter on Friday to the panel's chairman, Rep. John A. Boehner, Republican of Ohio, calling on him to hold a committee hearing on the issue.

The Education Department's annual revisions of the information used in the formula, which calculates how much money families can contribute to their child's education, are usually made with little fanfare. The tax data used are always a few years old, but typically this does not pose a problem. Financial-aid experts say an unprecedented problem arose this year because of recent drops and increases in tax rates. As a result, the data used this year, from 2000, do not reflect families' current tax burdens.

"All other things equal, families of the country's 16 million undergraduates will be expected to contribute about $12-billion more to their child's college education in 2004 than in 2003," said Brian Zucker, president of Human Capital Research, an Illinois-based consulting firm. Mr. Zucker cautioned that $12-billion was a ballpark figure, but said the actual amount was "absolutely not less than $10-billion."

Education Department officials said that the tax data they used were the latest available, and that the department is required by law to update the tax tables in the formula each year. They also said that their adjustment would not have a negative impact on students. Sally Stroup, the department's assistant secretary for postsecondary education, said in an interview that most Pell Grant recipients would not be affected, and that any financial burdens caused by the tax data would be offset by changes to other data used in the formula, such as family income.

While the Times reported that the department considered Human Capital Research's estimates "generally sound," Ms. Stroup and other department officials told The Chronicle that although some individuals in the department were familiar with the consulting firm's methodology, its estimates were incorrect.

When pressed to provide a more accurate estimate, department officials demurred, saying it was impossible to predict.

Nonetheless, other financial-aid experts seemed to unanimously agree that the change compounds existing financial burdens for students and their families. Across the country, states are spending less on higher education, while colleges are increasing tuition and decreasing institutional financial aid.

"The new table makes it seem like a family has more income than they actually have," which could disqualify students for Pell Grants, loan subsidies, and institutional aid, said Brian K. Fitzgerald, staff director of the Advisory Committee on Student Financial Assistance.

The independent committee was established under the Higher Education Act of 1965 to advise Congress and the Education Department on student financial-aid policy, but Mr. Fitzgerald said that it was not consulted on this issue. He said the department could have chosen not to adjust the rates, which he said was done in the 1980s. The department could have also made state-by-state adjustments, he said.

Many higher-education officials didn't expect a routine, annual update like this to become a controversy, said Pat Callan, president of the National Center for Public Policy and Higher Education. In a different economic climate, it may have gone unnoticed, he said, but this time, "it's just one more piece of bad news in a year that's full of them."