​WASHINGTON—The Consumer Financial Protection Bureau roughly doubled the number of enforcement cases it brought last year as the federal watchdog stepped up its scrutiny of industries including credit cards, auto lending and debt collection.

CFPB officials said that in 2015, the bureau handled 59 cases in which companies settled allegations of wrongdoing and 11 cases that led to lawsuits. That compares with 23 settlements and 11 lawsuits for 2014, and 21 settlements and seven lawsuits for 2013.

The sharp increase reflects the growth in the number of investigators, examiners and administrative staff, as well as maturing of the bureau's practices and policies four years after it was established under the Dodd-Frank financial overhaul law, said Tony Alexis, the CFPB's director of enforcement.

In an interview, Mr. Alexis declined to say whether the bureau's activities would continue to grow at a similar pace in 2016, but he said the agency's supervision and enforcement operations are now "fully functional." He told a legal conference Friday that the CFPB will be particularly active this year, enforcing rules in areas such as debt collection, mortgage servicing and student loan servicing.

The enforcement division, he said, increasingly relies on a bureau-wide process of scrutinizing financial institutions and their practices and products, looking for the "riskiest behaviors in which consumers can be hurt very quickly in a very profound way."

Last year's cases resulted in $6 billion in relief for consumers as the compensation for damages, and $1 billion in restitution as unlawfully obtained gains were forfeited and returned to consumers.

"We have muscle memory now built into our programs," Mr. Alexis said.

Contributing to the steep year-over-year increase are cases the bureau initiated a year or two ago while it was in growth mode, Mr. Alexis said. The average life cycle of the CFPB cases is about a year and a half, he said.

The vast majority of the cases involve alleged violations of so-called Udaap rules—unfair, deceptive or abusive acts or practices. Companies and their lawyers have complained that the Udaap rules are overly broad, making enforcement actions unpredictable.

According to an analysis of the bureau's 2015 activities by lawyers at Davis Wright Tremaine LLP, alleged Udaap violations accounted for three-quarters of all enforcement actions by the bureau.

"It is less helpful for the CFPB to define Udaap through enforcement rather than through rule making. It would be more efficient if the CFPB tells the industry what it wants by promulgating rules or issuing agency guidance," said Jenny Lee, a partner at Dorsey & Whitney LLP and a former CFPB enforcement attorney. She describes the agency as the "most litigious federal regulator facing the financial services industry."

Still, lawyers say the CFPB has begun to show more flexibility in allowing companies to resolve issues through inspection and informal dialogue. For example, there have been more cases where companies that voluntarily disclosed problems and their solutions avoided public embarrassment—and damage to their reputations. "More recently, there is a trusting relationship between the institution and the bureau," Andrew Sandler, partner of BuckleySandler LLP, said at the conference.

Spending by the CFPB's supervision, enforcement and fair lending division totaled $140.79 million for the year ended Sept. 30, up 3.7% from a year earlier. The division accounted for more than a quarter of the bureau's $524.4 million annual budget, according its annual report submitted to Congress last month.

Responding to the bureau's stepped-up enforcement, some big law firms are hiring more lawyers with expertise in consumer financial products, including former CFPB employees like Ms. Lee.

Covington & Burling said last week it had formally established a group focused on CFPB issues, as it hired Eric Mogilnicki, a former senior lawyer at the Federal Trade Commission and previously an assistant attorney general in Massachusetts with a track record of working with companies supervised by the CFPB.

Write to Yuka Hayashi at yuka.hayashi@wsj.com

(END) Dow Jones Newswires

January 11, 2016 18:15 ET (23:15 GMT)