Massachusetts credit unions are increasingly gaining a larger share of the market and an unfair advantage by claiming that they are serving low-income customers, according to a study released by a major competitor: the state’s community banks.

Since 2012, the number of Massachusetts credit unions that have earned a low-income designation that allows them to exceed regulatory limits on riskier, more profitable business loans and take in deposits from nonmembers has spiked, from just shy of a dozen to 57, according to the report.

To win the designation, credit unions must show that more than 50 percent of their members are low-income. They are allowed to count high school and college students in that tally, which community banks say is unfair.

“This ‘low-income’ designation is a significant loophole that could become a greater risk if these institutions are allowed to expand exponentially with no limits on commercial lending or membership,’’ said Dan Forte, president of the Massachusetts Bankers Association, which commissioned the study. He declined to say how much the association paid for the study.

The report is the latest volley by the bankers association in its long-running skirmish against the state’s 177 credit unions, which are nonprofit and exempt from paying state and federal corporate taxes.

Massachusetts community banks have bristled in recent years as credit unions have pushed to expand their membership rolls and lobbied for legislative changes that would allow them to accept deposits from public agencies, including school districts and cities — long a mainstay of local banks.

Credit union membership in Massachusetts increased by 24 percent between 2001 to 2014, according to the report. Credit unions encouraged consumers upset with banks during the financial crisis to join them. They have also eased their membership restrictions and increased their lending for automobiles and college educations, bringing in more customers.

The bankers association argues that credit unions should not enjoy tax-exempt status if they increasingly look like banks.

Credit unions hold $34 billion in assets, a fraction of the $376 billion in the state’s banks. But they do provide consumers more options and in some cases lower interest rates on loans, said Paul Gentile, president of the Cooperative Credit Union Association.

For most credit unions, the low-income designation is a marketing tool, a way to tout their services to a community, not a growth strategy or a tactic to circumvent lending restrictions, Gentile said.

“It’s a real badge of honor and pride,’’ Gentile said.

The National Credit Union Administration, the industry’s chief regulatory body, has made it easier in recent years for institutions to earn the low-income designation and has promoted it nationwide. As a result, 2,369 credit unions are designated as serving low-income customers, more than double the 1,100 institutions with that title in 2012, said John Fairbanks, a spokesman for the federal regulator.

In Massachusetts, 32 percent of the 177 credit unions have low-income designation, and include some of the largest institutions, such as Chelsea-based Metro Credit Union and Greylock Federal Credit Union in Pittsfield, along with the Harvard University Employees Credit Union.

Brian Gottlob, a principal of PolEcon Research, a New Hampshire consulting firm who authored the report, said that credit unions being able to raise their percentage of low-income members by counting students creates an unfair advantage.

Gottlob questioned how well some of the credit unions, especially the larger ones, are serving low- and moderate-income consumers. For example, both banks and credit unions make a similar percentage of their home loans — about 32 percent — to borrowers of low and moderate incomes, Gottlob said.

The benefits of the low-income designation are “not necessarily about serving low-income individuals,’’ Gottlob said.

But credit unions argue that college students are key members who are struggling financially with student loan debt.

“We’re not going to kick out college students. If they’re in your field of membership, they’re in your field of membership,’’ Gentile said. “Consumers in Massachusetts benefit from the existence of credit unions. We serve young college students as well as the older members of the Commonwealth.’’

Deirdre Fernandes can be reached at deirdre.fernandes@globe.com. Follow her on Twitter @fernandesglobe.