Save Our Skyline, a recently formed coalition of Cambridge citizens, started a petition last week to block parts of a City Council ordinance that the group says will result in the placement of large corporate signs on the city’s skyline.

The ordinance, passed by a vote of six to three by the Council last Monday, would allow business owners who control at least 25 percent of a building’s leasable space to post signs on its exterior without special permission from the City.

Save Our Skyline says that big landlords and politicians gain from the new ordinance, while putting small businesses at a disadvantage and potentially blighting the Cambridge skyline.

But according to City Councilor Leland Cheung, “[the new ordinance] is actually stricter than before.”

“There is a lot of misinformation out there,” Cheung said, adding that although the previous zoning laws limited the size of signs, the City Council frequently granted exemptions to the rule.

Opponents of the measure contend that big businesses will benefit from the new regulations, by, for example, allowing Microsoft to erect a sign that they say will allow the company to “brand the Cambridge riverfront.”

According to an attorney who has represented Microsoft in the past, the company is not involved in the initiative.

This is “completely untrue,” said James J. Rafferty, who claims Microsoft as one of his clients but does not represent the company in the matter. He called the petition drive by Save Our Skyline a “complete misrepresentation” of what the City Council has decided upon.

If 12 percent of registered voters in Cambridge sign the petition by October 14, the City Council will place a measure on the ballot for voters to decide whether to allow the new regulations to remain in place.

The petition, available online, seeks to prevent a part of the measure that allows more prominent identification of large corporate buildings in the city “that commonly host companies and enterprises that contribute significantly to the city’s economic health and well being” from taking effect. It also opposes language that restricts this right to companies which hold 25 percent of the buildings’ leasable space, which they say disadvantages small businesses.

Previously, the Cambridge Board of Zoning Appeals had approved signs on an ad-hoc basis. Under that system, the City Council would decide if a business or organization merited a sign larger than the legal restrictions.

According to Karen Schwartzman, spokeswoman for Save our Skyline, the new measure rescinds that process and waives the city’s 20-foot limit for signs on large buildings.

“Public space is sold and no benefit goes back to the citizens,” Schwartzman said.

But under the old system, multiple businesses in Kendall Square erected signs larger than what would be allowed under the new ordinance, Cheung said.

—Staff writer Rediet T. Abebe can be reached at rtesfaye@college.harvard.edu.  —Staff writer Sirui Li can be reached at sli@college.harvard.edu.