Commercial signs could be plastered at the Golden Gate Bridge visitors center and the nearby plaza under a corporate sponsorship plan that took a step forward Friday.

The plan is designed to raise millions of dollars to help maintain and restore the bridge. If approved next month, it might also brand the buses and ferries operated by the Golden Gate Bridge, Highway and Transportation District.

It would not, however, involve signs on the bridge or toll booths. And, officials say, the bridge district would not directly endorse the products of the business partners. There are no plans to actually rename the bridge in honor of any of the Bay Area's homegrown, nationwide or multinational businesses.

Some directors, including San Francisco Supervisor Jake McGoldrick, voiced concern about the idea and how using such fundraising techniques might commercialize the historic bridge and tarnish its global reputation. Other board members asked questions about what the program would actually look like or entail in terms of displays of sponsorship logos. And they wanted information about the effectiveness of such campaigns elsewhere.

"I am unequivocally and unabashedly opposed to turning the Golden Gate Bridge, one of the most important cultural icons in the United States, into an advertising item or consumer target item," McGoldrick said after the meeting. "I think you might as well turn the cathedrals and synagogues into advertising opportunities. This would be as unacceptable."

McGoldrick, who described the 70-year-old structure as "the No. 1-rated bridge in the world by architects," added: "I just don't think you turn this into a crass commercial opportunity."

He also complained that a staff report about the project wasn't given to the committee until after Friday's meeting had begun, and that only an executive summary of the report has been made public.

"No one from the public had a copy of this. I've never seen something that so lacked transparency in all my years of being involved," the supervisor said. "I think that's a terrible abuse of the public process. The public doesn't know what's going on. There was not a single person from the public who spoke out for it."

Currie said the full report is protected by attorney-client privilege because it contains information that, if made public, could compromise the trade secrets of Bartram Sponsorship Strategies.

San Rafael Mayor Al Boro, a bridge board member in favor of the project, said the plan has been well thought-out.