SACRAMENTO (Reuters) - A California campaign finance regulatory agency can audit a last-minute $11 million out-of-state donation to a political action committee by a mystery group from Arizona, a judge tentatively ruled on Tuesday.

A state Superior Court judge in Sacramento wrote that Californians "will suffer irreparable harm" if the California Fair Political Practices Commission is not allowed to audit the donation from Americans for Responsible Leadership.

The commission sued the Arizona-based non-profit last week for access, ahead of the November 6 general election, to information about its donors to evaluate if their donations comply with California campaign finance laws.

The $11 million donation is one of the single, largest contributions in the 2012 election season in California, and is also the largest out-of-state contribution from one independent non-profit to another for the purposes of influencing an election, commission chairwoman Ann Ravel said last week.

The Arizona group donated $11 million to the Small Business Action Committee PAC on October 15, according to the lawsuit.

The donation was intended to help fuel efforts to defeat a tax ballot initiative sponsored by California Governor Jerry Brown, a Democrat, and support another ballot measure that would stop automatic paycheck deductions for political activities that is seen as a potential blow to labor unions.

(Reporting by Mary Slosson; Editing by Cynthia Johnston)