HARRISBURG — Social-service advocacy groups are fighting legislation to require Pennsylvanians to provide proof of U.S. citizenship before receiving government benefits because they believe the bill would deny critical services to the poor, the elderly and domestic-violence victims.

Under the legislation, residents 18 and older who apply for benefits such as welfare or Medicaid would have to show a driver's license, a U.S. passport or other identification card issued by the state or federal government or the military. They would also have to sign affidavits stating they are U.S. citizens or legal residents.

Supporters of the measure that was the focus of a Senate State Government Committee hearing on Wednesday say it will prevent illegal immigrants from taking advantage of taxpayer-subsidized benefits, driving up state spending.

But opponents argue it will only create more bureaucratic obstacles for hundreds of thousands of Pennsylvanians who need assistance, but lack proper identification.

"This bill is unnecessary, would foster an atmosphere of fear and confusion among immigrants, and would prevent poor and elderly Pennsylvanians from getting the benefits they need," Louise Hayes, an attorney with Community Legal Services in Philadelphia, told the committee.

The Senate's highest-ranking Republican, President Pro Tempore Joe Scarnati of Jefferson County, said he introduced the bill earlier this year in response to his constituents' concerns and what he said was the federal government's failure to address the problem.