The NFL has branded allegations from Jon Gruden as "entirely meritless" after it was announced the former Las Vegas Raiders coach is suing the league following his resignation last month.

Gruden resigned from his post of head coach on October 11 after an investigation into the Washington Football Team revealed numerous offensive emails he sent while working as a television analyst before returning to the coaching ranks. 

His exit came shortly after the New York Times released a story quoting from a trove of emails from the coach's personal account that included multiple racist, homophobic and sexist remarks.

On Friday, Gruden filed a lawsuit against the NFL and commissioner Roger Goodell in Nevada's District Court.

Gruden's attorney, Adam Hosmer-Henner, told NFL Network's Tom Pelissero that Gruden is alleging the league and Goodell sought to destroy his career and reputation through a "malicious and orchestrated campaign".

A statement from Hosmer-Henner read: "The complaint alleges that the defendants selectively leaked Gruden's private correspondence to the Wall Street Journal and New York Times in order to harm Gruden's reputation and force him out of his job.

"There is no explanation or justification for why Gruden's emails were the only ones made public out of the 650,000 emails collected in the NFL's investigation of the Washington Football Team or for why the emails were held for months before being released in the middle of the Raiders' season."

In response, NFL spokesman Brian McCarthy said in a statement: "The allegations are entirely meritless and the NFL will vigorously defend against these claims."