Some of the country’s largest collectors of personal data are rejecting assertions from critics that they are data brokers, as members of Congress, including Representative Edward J. Markey of Massachusetts, seek to regulate the lucrative brokering industry.

Earlier this year, Markey and other lawmakers, under the auspices of a bipartisan congressional caucus on privacy, queried nine data-collecting companies, including the country’s largest credit reporting firms. The move was part of a fact-finding process that could lead to new consumer protection rules.