HARRISBURG — Pennsylvania’s seven-week-old voter identification law was challenged in court Tuesday by 10 registered voters, including some who say they do not have photo IDs and cannot get the kind required because their birth states do not have their birth certificates on file.

The lawsuit, filed in the state’s Commonwealth Court, warns of widespread disenfranchisement that would only become evident on Election Day, when voters who don’t know about the law or didn’t read its fine print realize too late that they don’t have valid ID and don’t have time to get one.

In addition, the lawsuit challenges the notion advanced by the law’s supporters that the photo ID requirement is necessary to combat voter fraud and that the law’s provisions are broad enough to ensure that everyone who needs a photo ID to vote will be able to get one.

The law violates the state constitution’s “free and equal” elections clause and another clause that establishes qualifications to vote in Pennsylvania, says the lawsuit, which also seeks an injunction that halts the enforcement of the law.

In addition to the ACLU, lawyers from the Public Interest Law Center of Philadelphia, the Washington, D.C.-based Advancement Project and law firm Arnold & Porter are representing the plaintiffs. The National Association for the Advancement of Colored People, League of Women Voters and Homeless Advocacy Project joined the lawsuit.

Gov. Tom Corbett, a Republican, signed the bill March 14 — one of the nation’s toughest voter ID laws — after it passed the GOP-controlled state Legislature over the objections of Democrats.

Corbett administration officials say they believe the law will withstand a court challenge. The nine-member Commonwealth Court is composed of seven Republicans and two Democrats.

Opponents of the law call it a throwback to the now-unconstitutional poll taxes and literacy tests designed to discriminate against poor and minority voters and a thinly veiled attempt to defeat President Barack Obama in the Nov. 6 election, when Pennsylvania, historically a swing state, is again expected to be a high-profile battleground.

Republicans, who for years have harbored suspicions of widespread voter fraud in the Democratic bastion of Philadelphia, say the law is a common-sense measure to ensure the integrity of the balloting and that photo IDs are regularly used in day-to-day activity.