Lobbyists from 26 interest groups, ranging from labor unions to corporations such as Wal-Mart and Proctor & Gamble, filed 76 reports showing they had tried to influence a bill before the Legislature that would have raised the state’s minimum wage last year.

After Gov. Paul LePage vetoed the measure, the debate shifted to the city of Portland, where Mayor Michael Brennan has introduced a proposal to raise the minimum wage in Maine’s largest community.

Who’s lobbying Brennan and the City Council on the issue?

No one but Brennan and the councilors know for sure, because Portland has no lobbying disclosure rules.

The same is true for South Portland, where the City Council wrestled this year with a so-called Clear Skies ordinance, a zoning change designed to block the potential shipment of tar sands oil from a pipeline to the city’s waterfront.

South Portland Mayor Linda Cohen says advocates from both sides of the tar sands issue were active in the city, where the ordinance proposal emerged after local voters rejected a ballot question to ban the oil shipments. But no reporting requirements are in effect.

Brennan, who was a state legislator for 13 years, said he often meets with lobbyists from an array of organizations.

“Quite frankly, until you just mentioned it, I never thought of it as a problem or an issue,” Brennan said in an interview. “Maybe it’s because I spent so much time in the Legislature and it was such a common practice that I didn’t find anything unusual about it at the municipal level.”

But advocates for transparency in government say the failure to require lobbying disclosures makes it hard for citizens to know who’s trying to influence elected officials, at a time when well-funded national groups are pouring millions of dollars into state and local politics.

Emily Shaw, a national policy manager with the Sunlight Foundation, a Washington, D.C., nonprofit that advocates for transparency in government, noted that campaign finance laws show how outside groups are spending at record levels on state and sometimes local elections.

But she said there’s no way to determine if those same groups are funneling money into lobbying campaigns that target local ordinance debates.

“It’s a stickier thing to argue, but we suspect that it’s the case,” Shaw said. “At any rate, it’s something that people need to know about.”

Maine law defines lobbying as communicating directly with state-level officials “for the purpose of influencing any legislative action or with the governor or the governor’s Cabinet and staff for the purpose of influencing the approval or veto of a legislative action when reimbursement for expenditures or compensation is made for those activities.”

State House lobbyists must file reports that disclose their activity if they engage in paid advocacy for more than eight hours a month. Lobbyists don’t have to say exactly how much they spent advocating for or against an individual bill unless they spend more than $1,500 on that one bill in a month.

That means the exact amount of lobbying dollars spent on many individual bills is unknown.

Some states, like New York, also require lobbyists who operate in larger municipalities to register, and in some cases disclose compensation and meetings with elected officials. In 2005, Portland, Oregon, adopted a sweeping transparency ordinance that required lobbyists to register with the city, and city councilors to post their meeting calendars online every three months.

But according to the National Conference of State Legislatures, most states have no laws on municipal lobbying, leaving the disclosure and registration of lobbyists up to individual cities and towns.

No Maine community has a lobbying disclosure rule, and the only time the state imposes a reporting requirement on cities and towns is when a community with more than 15,000 residents takes up a local referendum question – such as the November 2013 tar sands ballot measure in South Portland.

Finance reports filed in that campaign show that various groups and individuals spent $800,000 on advertising and other means of swaying voter opinion on the issue. Much of the money came from the American Petroleum Institute, the national oil industry trade group that spent $9.3 million lobbying Congress in 2013.

After the question was narrowly defeated at the polls, South Portland officials decided they wanted to craft an ordinance that would heal divisions in the city by preventing the future movement of tar sands oil without harming the petroleum business that has operated there for decades.

But unlike the referendum campaign, there were no requirements to disclose who was lobbying the seven City Council members as they developed the ordinance and finally approved it on a 6-1 vote in July.

Jerry Jalbert, former South Portland mayor, said he had lunch with paid lobbyists on both sides of the issue during the tar sands debate. He said he paid for his own meal on such occasions.

Cohen, a city councilor and the current mayor, said she was approached numerous times by advocates from both sides hoping to meet with her about the tar sands ordinance. She said she refused to meet privately with any group while the council was drafting the measure.

“I think all councilors were lobbied,” she said. “My philosophy is that I wasn’t going to get accused of favoring one side over the other.”

Cohen is a former Portland city clerk, and while she held that post she supported adoption of the state requirement that cities and towns collect campaign finance reports on local referendum questions.

“We were starting to see some casino ideas coming in, and people wanted to know where that money was coming from,” she said.

But Cohen isn’t sure there’s the same public interest in requiring lobbying disclosures when there’s no ballot question at stake. Neither are some local officials.

Portland City Councilor David Marshall said councilors quickly learn the handful of lobbyists who regularly approach them.

“I think if you ask councilors who are around for a few months, they know who is trying to influence them,” he said.

Marshall acknowledged that the public may not know that paid advocacy is happening.

“From a policymaker’s perspective, I can say that it (disclosure) wouldn’t hurt, but it may not be necessary,” he said. “From a citizen’s perspective, it could be more helpful because they don’t know who the regulars are and they may not be catching on to the dynamics.”

Cheryl Leeman, who stepped down recently after serving on the Portland City Council for 30 years, said lobbying “goes with the territory.”

“It seems to take a different shape and form at the local level, compared to the state level,” she said. “I think it’s more transparent.”

Still, she said, the council seemed to be dealing with “more issues that are more federal and state in nature. Not that it didn’t happen before, but it’s different now.”

Examples include the minimum wage proposal, which is a key issue for organized labor and the Democratic Party, and the city’s bans on polystyrene foam containers and plastic shopping bags, which reflect the interests of national environmental groups.

The polystyrene foam and plastics ordinances drew opposition from Maine business groups and even Gov. LePage. A campaign called Cleaner Portland launched Web advertisements and other communications to oppose the measure. Cleaner Portland is connected to Americans for Tax Reform, a nonprofit headed by conservative activist Grover Norquist that had $4.3 million in revenue in 2013, according to filings with the Internal Revenue Service.

Christopher O’Neil, of the Portland Community Chamber of Commerce, said lobbyists from the American Plastics Council and other national trade groups asked for meetings with Brennan, the Portland mayor, and members of the City Council.

“How much it cost them was probably insignificant to them, but it was likely a lot relative to what is customary for Portland ordinances,” O’Neil said.

Backing the ordinances were other outside groups, including the California-based nonprofit Surfriders Foundation, which had $6.8 million in revenue in 2012, the most recent figure available.

Brennan said he held meetings with a number of the groups.

O’Neil is considered Portland’s most active lobbyist, and he is representing the chamber and its business members in opposition to the proposed minimum wage increase, which is still under City Hall review.

O’Neil is open about his advocacy efforts at Portland City Hall – to a point. He recalled an instance when a former councilor asked him during a meeting how much he was being paid to lobby the council.

“If you asked me the same question, I’d give the same answer,” he said. “It’s my business. I am influencing public policy and I understand why people would ask, but until such time that there’s a requirement to disclose that stuff, I can’t.”

Shaw, the policy director at the Sunlight Foundation, said it’s important that cities and towns have such requirements so citizens know who is trying to influence local officials. And she noted that technology makes the job of gathering and sharing such information much faster and cheaper.

“Because it is now so easy to transmit information over the Internet, the old excuse that it was too much cost to collect and require it for a resource that very few people would ever end up looking at is moot now,” she said.

But requiring lobbying disclosure will require more convincing among local officials.

“Maybe we’ll get to a point where something will happen and everyone will be like, ‘OK, now’s the time we need to do this. This is really important,’ ” said Marshall, the Portland councilor. “It just hasn’t really raised up to that level.”