The NFL is under fire after a new book blamed the league for carrying out a two-decade campaign to cover up research linking football to brain damage.

"League of Denial: The NFL, Concussions and the Battle for Truth" says that the NFL used its power to crush a mounting pile of evidence and once even tried to retract published work from concussion researchers.

The book accuses former NFL commissioner Paul Tagliabue of being the driving force behind the cover up process and that his successor, Roger Goodell, the current commissioner, has done the same.

The book also says that the league started making disability payments to former players as early as 1999 but that it would be another ten years before the NFL would admit a link between brain damage and playing football. It was just a year later in 2000, the book said, that some of the nation's top neuroscientists notified the league that playing football can lead to depression, memory loss, dementia and brain damage. The book also says that the current commissioner, Goodell, was told in 2007 about more links to football and brain damage, but he kept quiet. It wasn't until three years later that Goodell opened up about the issue.

According to ESPN, league executives refused to cooperate with the book.

"As the crisis escalated, the NFL tried desperately to regain control of the issue and contain damage to its brand," ESPN said in describing the details from the book. "Before an October 2009 hearing on football and brain injuries conducted by the House Judiciary Committee, the NFL lobbied successfully to prevent Goodell from testifying on the same panel as the father of a high school quarterback who had died after sustaining a concussion."

It was just in August that the NFL allegedly pressured ESPN to end a partnership with PBS after it was revealed that The Worldwide Leader in Sports was going to help produce a documentary highlighting the health issues behind playing football.