SAN DIEGO, Calif. (CBS 8) - A state political watchdog agency has issued a warning letter to campaign supporters of county supervisor Bill Horn.

During the 2006 election, developers and their associates paid more than $167,000 to send out a political mailer that helped supervisor Horn win reelection.

It was sponsored by a group called Voters for Responsible Government, based in Orange County.

The Fair Political Practices Commission says the slate mailer in question violated state law because the mailer named several candidates without their permission.

Required campaign disclosure filings also failed to report employer information for three contributors, according to the warning letter.

Orange County developers contributed heavily to the slate mailer, including $20,000 from Stonegate Development , $20,000 from Newland Communities, and $20,000 from political consultant Steve Sheldon of Newport Beach.

Stonegate, Newland and Sheldon are all associated with the failed Merriam Mountains housing development that had been planned for Bill Horn's district.  The county board of supervisors voted down Merriam Mountains this week on a three to two vote.  Supervisors Bill Horn and Greg Cox voted in favor of the development.

The warning letter was addressed to Scott Hart, a Newport Beach political consultant listed as the treasurer for Voters for Responsible Government.

The FPPC launched an investigation following complaints by community activists.

The complaints alleged Horn was involved in producing and distributing the slate mailers.

Horn has said he had no advance knowledge the mailer was being sent out.  The FPPC warning letter does not allege any wrongdoing on the part of supervisor Horn.