(CNN) The National Rifle Association is beating back a new round of criticism from some of its own board members.

In a letter to NRA leadership Monday, four board members called for an "outside professional to conduct an independent, internal investigation and confidential audit into the allegations of financial misconduct."

They are also calling for a review of the millions of dollars the NRA has shelled out to outside counsel, Brewer Attorneys. They want both issues investigated by an outside committee that will report its findings to the full NRA board.

"With this degree of scrutiny and transparency, the Board can fulfill our legal obligations, remove all doubt regarding our Association's direction, and allow us to return to our mission of protecting our Second Amendment," according to the letter from Sean Maloney, Timothy Knight, Esther Schneider and retired Lt. Col. Robert K. Brown.

Their full letter was posted by the Ammoland website, and the authors shared it on their Facebook pages.

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