A lawsuit against polygamous leader Warren Jeffs is taking aim at the group's longtime Utah law firm, arguing attorneys created a veneer of legality that helped leaders perpetuate abuses like child labor and underage marriage.

The firm Snow, Christensen and Martineau denied the allegations in scathing terms Thursday, saying lawyers like Rod Parker were simply doing their jobs and can't be held responsible for anything Jeffs did.

The firm "is no more responsible for Warren Jeffs' actions than the doctor who kept him healthy," defense attorneys wrote in court documents.

But the lawsuit claims attorneys helped Jeffs devise legal strategies for tightening his control over the group after he took over leadership from his father in the late 1990s. Jeffs used that power to marry and sexually assault underage girls as well as arrange other underage marriages, the suit says.

Jeffs is serving a life prison sentence after being convicted of sexually assaulting girls he considered wives. He no longer has a lawyer, and the Fundamentalist Church of Jesus Christ of Latter-Day Saints doesn't have a phone number to contact for comment.

The lawsuit filed by more than 20 former FLDS members says the law firm helped burnish the group's credentials as a maligned religious group as cover for the abuses.

The firm "worked unceasingly for years to evolve, protect, strengthen and tighten the systematic control and to facilitate and enable Jeffs' ongoing criminal use of that power," the suit alleges.

The firm earned millions in legal fees, paid in large part with money earned by forced child laborers, the suit said.

The firm and Parker call many of the allegations "utterly nonsensical."

It strongly denied being involved with anything illegal and condemned the wrongs the plaintiffs say they suffered under Jeffs, including being forced into marriage and separated from their families.

The well-known Salt Lake City law firm said that while lawyers don't necessarily agree with their clients, the well-established principle that people are entitled to legal representation is older than the Constitution. Snow, Christensen and Martineau no longer represents Jeffs or the FLDS.

The private lawsuit comes as the federal government wages fights on multiple fronts to rein in the secretive Jeffs-led group.

Jurors in Phoenix found in March that the twin polygamous towns on the Utah-Arizona border violated the constitutional rights of nonbelievers by denying them basic services such as police protection.

Last month, a judge in Utah found FLDS children were forced to work long hours, sometimes with little food, at a pecan farm in 2012.

A federal grand jury also has indicted several church leaders on charges of conducting a multimillion-dollar food stamp fraud scheme. Leader Lyle Jeffs is on the run after escaping home confinement in that case.