Consumers who allege Client Services Inc. sent improper letters to collect on Capital One credit card debts may proceed as a certified class, a federal court said June 7.

Whether the form letter violated the Fair Debt Collection Practices Act is a question common to all class members, Judge William C. Griesbach wrote for the U.S. District Court for the Eastern District of Wisconsin.

The class includes more than 6,800 consumers in Wisconsin.

Jacquelyn A. Vandehey alleges the collection letters...