National Football League officials improperly sought to influence a government study on the link between football and brain disease, according to a senior House Democrat in a report issued Monday.

New Jersey Rep. Frank Pallone says the league tried to strong-arm the National Institutes of Health into taking the project away from a researcher that the NFL feared was biased.

The NFL had agreed to donate $30 million to the NIH to fund brain research but backed out after the institutes refused to take a $16 million grant away from prominent Boston University researcher Robert Stern. He's a leading expert on the link between football and brain diseases such as chronic traumatic encephalopathy. Taxpayers are instead bearing the cost.

The NFL denied Pallone's finding.

"We are reviewing the report but categorically reject any suggestion of improper influence," NFL spokesman Brian McCarthy said Monday.

Some of the members of the NFL's Head, Neck, and Spine Committee who opposed Stern had also sought the grant.

Critics say the NFL has long downplayed the link between football and brain damage, alleging that an NFL committee on brain injury had long ignored or minimized the link between repetitive head trauma and brain damage.

"This investigation confirms the NFL inappropriately attempted to use its unrestricted gift as leverage to steer funding away from one of its critics," Pallone said.  "Since its research agreement with NIH was clear that it could not weigh in on the grant selection process, the NFL should never have tried to influence that process."

Pallone initiated the investigation after ESPN reported that the NFL had backed out of funding the NIH study because of its objections to Stern.

Stern has been vocal about the connection between football collisions and brain damage and filed a declaration opposing a settlement between the NFL and former players, fearing that deserving players would not be compensated.

NFL Medical Director Dr. Elliot Pellman emailed the executive director of the Foundation for the National Institutes of Health, which raises private funding for NIH research, and said the league had significant concerns regarding Boston University "and their ability to be unbiased and collaborative." He asked the FNIH official, Dr. Maria Freire, to "slow down the process until we all have a chance to speak and figure this out."

The NFL's email was forwarded to Dr. Walter Koroshetz of the National Institute of Neurological Disorders and Stroke at the NIH, who was in charge of selecting a recipient for the grant. He responded that there was "lots of history here" and that the NFL's had problems because the research would be "led by the people who first broke the science open, and NFL owners and leadership think of them as the creators of the problem."

Pallone found that NIH officials acted properly in not bending to the NFL's will. NIH policy prohibits donors from influencing which researchers receive grants, a process that relies on peer review.