The Charity Commission and the Cabinet Office will look into a complaint that commission board member Gwythian Prins broke Cabinet Office impartiality rules.
Andrew Purkis, a former commission board member, wrote to William Shawcross, the regulator's chair, claiming that Prins's essay Beyond the Ghosts - does EU membership erode Britain's global influence?, published by the group Historians for Britain, was a "multiple breach" of the Code of Conduct for Board Members of Public Bodies.
Purkis sent his letter to Paula Sussex, chief executive of the commission, and Matthew Hancock, the Minister for the Cabinet Office. Purkis told Third Sector the essay was "an extraordinary example of what you should not do if you're a member of a public body".
He called for Shawcross to consider Prins's position. He said: "When I was on the board, none of us would have dreamed of publishing something like that. I think it is a serious issue for consideration by the chair as to whether Prins, with his strong, militant views about current political issues, is the right sort of person to be bound by the requirements of a public body."
William Shawcross, chair of the commission, said in a statement that it would consider the issues raised in Purkis's complaint in consultation with the Cabinet Office. Shawcross said he took the issue of the independence of the commission "extremely seriously".