The lawsuit names Houston city and its police department

The officers are suing Houston and its police department, claiming status and pay have been reduced.

The department imposed the ban in 2005, saying gas masks could not be sealed over facial hair in bioterror attacks.

The officers say the ban is unfair on those with a particular skin condition that reacts to shaving and primarily affects black men.

The condition is called pseudofolliculitis barbae and sufferers who shave can be subjected to rashes, ingrowing hairs and severe irritation.

Two of the plaintiffs, Sgts Shelby Stewart and Kenneth Perkins, said they wore goatees because of the condition.

They said it affected more than 100 policemen in the department.

Police review

Sgt Stewart, who has been on the force for 26 years, told the Houston Chronicle newspaper: "When they took us out of uniform and told us we couldn't work second jobs in uniform, that meant that we had to take a financial hit that most officers would not take."

The lawsuit argues the ban disproportionately affects black officers.

Sgt Stewart said: "We made decisions that we had to make based on civil rights."

Houston police denied the reassignments were demotions and said it had changed its policy over the issue.

Police lawyer Craig Ferrell said officers who were unable to shave would be now allowed to wear a special mask over their beard.