A US judge has called the military's gay ban unconstitutional.

The federal judge declared it is unconstitutional for openly gay service men and women not to be able to play a part in the military.

US District Judge Virginia Phillips said she would issue an order to stop the government from enforcing the "don’t ask, don’t tell" policy, saying the practice continues to violate the First Amendment rights of gays and lesbians.

In her ruling, Judge Phillips said the "don’t ask, don’t tell” policy, which prohibits the military from asking about sexual orientation but requires discharge of those who acknowledge their homosexuality, has a "direct and deleterious effect" on the armed services.

The ruling was brought down after a suit was filed by current and former military members, seeking an injunction to stop the ban’s enforcement.

The federal government will now have to respond to the ruling.