Crushing student debt was a flash point on the campaign trail, as students complained that loans had diminished their career prospects. The issue helped fuel Bernie Sanders’s campaign in the Democratic primaries, and sparked discussions about reining in college costs. Total outstanding student loan debt hovers at more than $1.4 trillion. Student loan debt has surpassed credit card and auto loan debt.

Navient, which plans to fight the lawsuits, denied all wrongdoing.

“The allegations of the Consumer Financial Protection Bureau are unfounded, and the timing of this lawsuit — midnight action filed on the eve of a new administration — reflects their political motivations,” Patricia Nash Christel, a company spokeswoman, said in a written statement. “We will vigorously defend against these false allegations.”

Regulators and consumer groups have long complained about widespread abuses in the student loan market, but Wednesday’s coordinated state and federal action, which stems from investigations that began about three years ago, is a legal attack that is likely to resonate throughout the industry.

Navient is accused of deliberately steering borrowers away from income-based repayment plans that could have lowered their loan costs — in order to maximize its own profits. Enrolling customers in such plans can be time-consuming and complex, and Navient’s compensation system for its customer service representatives encouraged them to push struggling customers toward other options, according to the bureau’s complaint.

Derek Smith said he is one such borrower. In 2011, when his loan payments kicked in, he was living in a homeless shelter in Boston. He had no job and three children.

Mr. Smith was exactly the kind of former student who should have had his payments reduced, according to Persis Yu, director of the Student Loan Borrower Assistance Project at the National Consumer Law Center. But that never happened, she said. After struggling for two years to make a dent on his loans, Mr. Smith defaulted and his wages from a new job were garnished. Collection calls poured in.