Opening a legal front in an ongoing battle, the Archdiocese of Philadelphia's social services agency has accused the city of religious discrimination for suspending its foster-care placement contracts because the agency refuses to place children with same-sex couples.

In a federal lawsuit filed late Wednesday, lawyers for Catholic Social Services and three foster parents are asking a judge to order the city to resume its contracts and award damages. It said the March 15 decision halting future placements puts politics over children.

"Unsurprisingly, the city's actions are creating a severe human cost," the suit says. "Available foster homes are sitting empty."

City officials on Friday would not comment on the lawsuit but defended their decision to stop foster-care placements through the church agency. "As Catholic Social Services works on the city's behalf, we cannot allow discrimination against qualified couples who are ready to take on this important role simply because of who they are," said a statement from spokeswoman Deana Gamble.

Catholic Social Services and a second faith-based agency, Bethany Christian Services, came under fire after the Inquirer and Daily News reported in March that Bethany had turned away a same-sex couple who sought to become foster parents.

City officials said such a stance violates its contract rules, which prohibit discrimination against individuals based on sex, gender identity, or sexual orientation. They suspended the contracts and launched a Human Relations Commission investigation into the practice. At the same time, the city put out an urgent call for about 300 more foster families.

The two agencies together collect about $3 million a year from the city for foster-care reimbursements, and had placed more than 230 children in city foster homes.

Bethany is not a party to the legal fight, but in a statement Friday said, "It is our hope that government and community organizations can work together in partnership to be part of the solution, offering services to vulnerable children and families."

The lawsuit was filed by Becket, a Washington-based law firm that specializes in religious liberty cases. The Philadelphia foster parents named as plaintiffs are Sharonell Fulton, Cecelia Paul, and Toni Lynn Simms-Busch, who the suit says will no longer or will unlikely be able to foster children if Catholic Social Services is forced to close its program.

According to the suit, Paul has worked with Catholic Social Services for 46 years and has fostered 133 children. She had been honored by the city in 2015 as one of its Foster Parents of the Year for her care.

Simms-Busch previously worked as a foster-care social worker with a private agency and later as a child-advocate social worker who spent four years working at the Defender Association of Philadelphia, according to the lawsuit. She now cares for two very young foster children and chose to work with Catholic Social Services because of the agency's high level of care and her religious beliefs, it says.

Fulton has fostered more than 40 children for more than 25 years and shares the religious beliefs of Catholic Social Services, the suit says. She has cared for children with significant medical needs and is caring for two special-needs foster children.

"If the city terminates its contract with Catholic Social Services, or refuses to renew the contract in June, Ms. Fulton's two current foster children will be immediately transferred away," the suit says.

Ken Gavin, a spokesman for the Philadelphia Archdiocese, said the archdiocese was "extremely disappointed" with the March decision, at a time that he said the city is "in a foster care crisis."

"We hope and pray for relief from the courts so that we can continue to serve children and young people in need," Gavin said in a statement.

One of the Becket lawyers, Lori Windham, noted that the agency's contracts with the city were not suspended because of any complaints by individuals about the service provided by Catholic Social Services.

"The city is discriminating against them [Catholic Social Services] because of its religious belief," she said Friday. "The city is refusing to place children with parents just because those parents choose to work with Catholic Social Services."

The lawsuit cites past U.S. Supreme Court decisions, including a 2017 decision in which the court held in favor of a Lutheran preschool that claimed religious discrimination after it had been denied a state grant for playground resurfacing.

Rue Landau, executive director of the Human Relations Commission, said the commission had been conducting an investigation to determine if Catholic Social Services' policies and practices have intentional or unintentional discriminatory effects.

She said Friday that the investigation has been stalled because of the lawsuit, but didn't elaborate, instead saying, "We are assessing our next steps in light of the litigation."