The city is going after illegal short-term vacation rentals across the island, in some cases using evidence gathered by neighbors to cite operators and order them to close down.

This year 57 citations have been issued, five warning letters have been sent and three notices are pending in Hau'ula, the North Shore and Kailua, city officials said. Fines start at $50, and can go as high as $1,000.

City ordinance requires owners to rent their properties for at least 30 days at a time or face fines.

"We've taken perhaps a slightly more aggressive approach where we think there might be some question," said Henry Eng, director of the city Department of Planning and Permitting. "We've investigated and where we find operations are being conducted that are not consistent with the land use ordinance, we've cited people."

One operator said a neighbor has gone too far.

Tricia Tatham, of Kailua, said when she bought her home near the beach two years ago, she intended to rent it out when she was visiting relatives on the Mainland. But a neighbor complained and a city inspector came to her home, so now she complies with the law. The rule allows owners to rent their home for 30 days or more, but she still gets complaints, visits from the inspector and warning letters.

"I informed my neighbor that there was a legal rental and they still called in," Tatham said.

Tatham said she was even told that she couldn't let friends stay at her home if she wasn't there.

"It's very confusing," she said. "We do need resolution. I want to be a good neighbor. I do want to comply, but I do own my home and I want to be able to rent it out however I see, with guidelines."

The city citations and letters follow a growing discontent with transient vacation units and bed-and-breakfast operations that neighbors say create noise problems and increase traffic.

At least two groups have organized around different sides of the dispute and have launched educational campaigns. Several City Council measures also have been introduced to address the problem.

A limit on bed-and-breakfast operations and transient vacation units was set in 1989 over a concern about their proliferation and impact on residential communities. An estimated 1,200 short-term vacation rental units are being operated without proper permits on the island.

The recent enforcement is a dramatic increase over last year.

"No warning letters (were issued) in 2004," said Art Challacombe, chief of customer service with the city's planning and permitting department. "We do not have anything in 2004 to compare."

Recently, the City Council addressed the issue with proposals that would allow for more bed-and-breakfast operations and would require operators who advertise on the Internet to place their license number on the Web. These measures are pending.

On occasion, the city also has written to real estate agents to advise them when it sees possible problems with the advertising of a property, Eng said.

"In those cases, it's trying to avoid a prospective problem," he said.

The city said neighbors have been helpful in collecting evidence against illegal operations, acting as the eyes and ears of the inspectors.

Threats of legalizing more bed-and-breakfast units led to the formation of Save O'ahu's Neighborhoods Hawai'i this year.

Larry Bartley, founding member of SONHawai'i, said the move would lead to a regulatory nightmare for the city because there's no way to determine who is in the home. Illegal transient vacation rentals would get bed-and-breakfast permits and continue to operate, he said.

The city's effort to go after illegal operations now is an important change, Bartley said.

"Now, DPP is becoming very proactive — rather than just responding to complaints they're going out and looking for information," he said.

David Bramlett, a North Shore resident, said the city should give enforcement more time to work before approving any new changes to the law, especially increasing the number of bed-and-breakfasts because people have lost confidence in the city's ability to control the industry.

"I say let that go for a year, 18 months, see how effective we can be," Bramlett said. "Then I think the community might have confidence in opening up some other alternative."

On the opposite side of SONHawai'i is Kokua Coalition, which wants a moratorium on citations and warning letters until a resolution can be worked out with all parties, said the group's Powell Berger. The group's Web site identifies it as a coalition of a variety of small-business people who support better regulations while recognizing vacation rentals and bed-and-breakfast hotels "are a key component to sharing the prosperity of the visitor industry."

Conflicts are pitting neighbor against neighbor, but Berger said she thought problems are isolated and the number of illegal units are exaggerated. Nevertheless, she would welcome improved regulation and enforcement in the industry, she said.

"So if there's a badly run, badly managed, bad neighbor kind of unit, it needs to go," she said. "We want a system that does that."