A federal appeals court on Thursday refused to block Obama administration regulations that were adopted to minimize conflicts of interest in the retirement-investment industry, a significant setback for financial planners, insurance agents and other advisers who said the rule will disrupt the marketplace.

The National Association for Fixed Annuities in November urged the Washington court to freeze for at least 10 months the April 10, 2017, start date of the new rule, which requires financial professionals who give retirement advice to put the best interest of their customers before commissions or fees. The U.S. Labor Department in April adopted the new regulations, a project more than six years in the making. Rules governing retirement investment advice had remained unchanged for decades.