In an effort to show a unified front in their campaign against the birth control mandate, 43 Roman Catholic dioceses, schools, social service agencies and other institutions filed lawsuits in 12 federal courts on Monday, challenging the Obama administration’s rule that their employees receive coverage for contraception in their health insurance policies.

The nation’s Catholic bishops, unable to reverse the ruling by prevailing on the White House or Congress, have now turned to the courts, as they warned they would. The bishops say the requirement is an unprecedented attack on religious liberty because it compels Catholic employers to provide access to services that are contrary to their religious beliefs. The mandate is part of the Obama administration’s overhaul of the health care system, which the bishops say they otherwise support.

Cardinal Timothy M. Dolan, whose archdiocese in New York is among the plaintiffs, said in a statement, “We have tried negotiations with the administration and legislation with the Congress — and we’ll keep at it — but there’s still no fix.”

The bishops rejected a compromise offered by President Obama in February that would have insurance companies — not the Catholic employers — pay for and administer the coverage for birth control. When some Catholic organizations broke with the bishops and greeted the accommodation positively, the bishops resolved that Catholic institutions must present a united front.