By Gary Robertson
RICHMOND, Virginia (Reuters) - A federal judge in western Virginia has certified as a class action a lawsuit filed by two Shenandoah Valley couples challenging the state's ban on same-sex marriages.
Friday's order adds to growing momentum to end the state's prohibition of same-sex marriage, with Virginia's new attorney general saying his office will no longer defend the ban.
U.S. District Court Judge Michael Urbanski said in the order that same-sex couples seeking to marry in the state as well as those married in states where gay marriage is legal could challenge Virginia's ban as a group.
Lawyers for the couples who filed the lawsuit estimate that there are about 15,000 same-sex households in Virginia, based on U.S. Census data.
The lawsuit seeks a declaratory judgment striking down Virginia's same-sex marriage laws and a permanent injunction barring their enforcement.
At the request of two same-sex couples involved in a parallel lawsuit in federal court in Norfolk, Urbanski's order excludes them from the class action to avoid interfering with their case.
Attorney General Mark Herring, a Democrat, said his decision not to defend the ban was aimed at putting Virginia "on the right side of history" and ending its legacy of opposing landmark civil rights rulings by the U.S. Supreme Court.
Republicans in Virginia's House of Delegates, who have threatened to impeach Herring, are trying to push through a bill that would permit them to hire their own counsel to defend the marriage ban. But even if approved, the bill would probably be vetoed by the Democratic Governor Terry McAuliffe.
The Virginia attorney general's decision not to defend the ban follows two Supreme Court rulings last year.
One struck down the Defense of Marriage Act, a law that denied federal benefits to legally married same-sex couples.
The other paved the way for gay marriage to resume in California. But those rulings did not address whether state bans on same-sex marriage were constitutional.
In 2006, 57 percent of Virginians voted in favor of the state's constitutional amendment prohibiting same sex marriages.
But a poll released last October by Virginia's Christopher Newport University showed that 56 percent of likely voters opposed the ban, and 36 percent favored it.
Seventeen states plus the District of Columbia recognize same-sex marriage, including eight states where it became legal in 2013. Thirty-three ban gay couples from marrying by state constitutional amendment, statute or both.
(Reporting by Gary Robertson; Editing by Jon Herskovitz; Editing by Lisa Von Ahn)