PITTSBURGH—Democrats on Allegheny County's elections board have announced that they plan to challenge Pennsylvania's GOP-backed voter identification law.

County Executive Rich Fitzgerald said Friday that the legal action to be taken next week will argue that the law is too expensive and difficult to implement in time for the November election.

The American Civil Liberties Union of Pennsylvania and others have already challenged the law on constitutional grounds, arguing that it makes it harder for some citizens to vote, especially the elderly and minorities. Backers say the law, similar to measures recently passed in other states, will reduce existing and potential voter fraud.

Fitzgerald—who was joined by more than a dozen other Pittsburgh, Allegheny County and state Democratic officeholders—said officials also believe that the law will make it more difficult for poor, minority and elderly voters with IDs to casts ballots.

"It's going to disenfranchise and deny an awful lot of people the ability to vote," Fitzgerald said.

He said, however, that the election's board lawsuit differs from the ACLU suit in arguing that the county does not have the money or time to train the 6,500 poll workers who staff the county's 1,300 polling places in new procedures required to check identifications and allow voters to use provisional ballots if they don't have proper ID.

Republican County Councilwoman Heather Heidelbaugh, who also sits on the elections board along with Fitzgerald and Democratic County Councilman John DeFazio, said she will oppose the lawsuit.

"I don't quite understand why we're spending lawyer resources on this," she said. "Why are we filing a lawsuit on the same topic when the ACLU has already done it?"

In a separate action, county controller Chelsa Wagner filed a friend-of-the-court brief supporting the ACLU suit, describing the new rules requiring poll workers to review photo IDs as an "unfunded mandate" that would cost counties millions, according to the Pittsburgh Post-Gazette. She called on the Justice Department—which has moved against voter identification laws in South Carolina, Texas and Florida—to bring similar legal action in Pennsylvania.