Council critic Bob Rush, a West Newport resident, filed a complaint in October and received a response this week.
Because the committee disclosed the printing costs in a campaign form filed late in the electoral season, the FPPC decided to issue just a warning this time, according to the letter.
Rush had criticized the chamber before the election because some of its leaders helped draft a ballot measure that allowed the city to fund chamber events, without any limits. The measure passed.
The city could now be potentially financing politicians, Rush said, because chamber funds and its political action committee funds were intermingled.
"There was never a separation," he wrote in an e-mail, adding that the city has now written a "blank check" to the chamber.
The mailer endorsed four City Council candidates: Nancy Gardner and Mike Henn, who were running unopposed, and Rush Hill and Leslie Daigle, who were running against Ed Reno and Mark Tabbert, respectively.
Luehrs also said he was not aware of the disclaimer requirement, but he would include it on future mailers.
Printing costs were disclosed when the committee received its printing bill, Luehrs said.
"I think that's pretty silly," he said. "It's just a function of timing."
The chamber's political action committee donated at least $1,000 each to the campaigns of Hill and Daigle in 2010. In 2006 it spent more than $22,000 to try to defeat Greenlight II, a slow-growth initiative.
Political contributions and chamber membership dues are kept in two separate accounts, Luehrs said in October. The chamber's nonprofit status restricts it from contributing to political candidates.