PORTLAND – Catholic Charities of Maine filed a federal lawsuit Friday against the city of Portland over its domestic partnership ordinance that restricts federal funding to the charity.

In a suit filed in U.S. District Court, Catholic Charities claims the city ordinance violates equal protection laws of the 14th Amendment and the federal Employee Retirement Income Security Act.

It further claims the ordinance is unfair because it applies only to organizations that receive federal Housing and Community Development funds from the city, but not the hundreds of companies and organizations that do business with the city.

Portland’s ordinance requires agencies that receive Community Development Block Grants through the city to offer their employees’ domestic partners the same benefits that spouses receive.

The city says the ordinance keeps public money from funding discrimination. But the charity contends it’s inconsistent with Catholic teachings on premarital sex and homosexuality.

“We are standing by our principles,” said John Kerry, chief executive officer of Catholic Charities of Maine. “We have 600 employees throughout the state, and the city does not have the right under the law to require us to design, implement and administer a special employee health benefit plan solely for those who work in Portland.”

Gary Wood, Portland’s city attorney, said Catholic Charities is entitled to grant money if it complies with the ordinance.

“We don’t agree with their position and we’ll defend our action in court,” Wood said. “That’s what courts are for. I’m sorry they’re taking the adversarial litigation route.”

The city passed its domestic partners law last May, and most organizations that receive the development grants from the city complied with the ordinance.

The Salvation Army, however, forfeited a $60,000 grant for its senior center and meals-on-wheels program rather than compromise its religious stand against unmarried couples living together.

Catholic Charities would have received $88,310 for two child care programs, homemaker services for the elderly and mental health programs. Those programs employ about 125 people.