Moniem El-Ganayni is an outspoken critic of the US government. Credit: K. SRAKOCIC/AP

An Egyptian-born nuclear physicist is suing the US Department of Energy over the revocation of his security clearance.

Moniem El-Ganayni worked from 1990 as a scientist at the Bettis Laboratory, a contract lab for the energy department near Pittsburgh, Pennsylvania, that works on nuclear propulsion. El-Ganayni, a US citizen since 1988, is an active member of the local Islamic community. He has been an outspoken critic of the Iraq war and the US government's treatment of Muslims, and was particularly critical of government efforts to recruit informants, according to his lawyer Keith Whitson, a partner at Schnader Harrison Segal and Lewis in Pittsburgh.

In May, the energy department revoked El-Ganayni's security clearance, in part because he was suspected of “conflicting allegiances”. Shortly thereafter, he was fired from the laboratory. El-Ganayni's suit, filed with the help of the American Civil Liberties Union, claims that the Department of Energy has violated his rights of free speech and freedom from discrimination.