ST. PAUL, Minn. — The state board that regulates political spending in Minnesota has issued new guidelines for donations to ballot measure campaigns, and critics say it could force some donors to stay on the sidelines in next year’s vote on the marriage amendment.

The Campaign Finance and Disclosure Board on Tuesday approved a new “statement of guidance” on how the state’s laws on political fundraising should be applied to ballot measure campaigns. The board says in some circumstances, groups funded by private donations that take sides on ballot measures will have to report the exact source of those donations with the state.

Some socially conservative groups pushing to ban gay marriage in the Minnesota Constitution say some of their donors may be reluctant to go public with their support.