In a formal complaint to Bruce County, two activist groups also say the mayors may have violated provincial laws by failing to document and publicize years of meetings with nuclear waste officials.
Those involved say nothing untoward occurred but the Southampton Residents Association and Save our Saugeen Shores see skullduggery in the highly charged search for a permanent storage site.
"The lack of transparency in reporting and timing of the release of information ... demonstrate a mission to keep Bruce County constituents uninformed during crucial decision-making processes," their complaint to the county sent Friday alleges.
Recent documents show the eight county mayors met 16 times with the Nuclear Waste Management Organization and Ontario Power Generation between 2005 and 2012 to discuss a proposed underground facility for low and mid-level waste.
Informal notes were kept for only eight of the meetings held between 2009 and 2012.
In early 2009, discussions also turned to finding a willing host community for high-level radioactive waste.
Notes of an Ottawa meeting in February 2010 show then Brockton mayor Charlie Bagnato "felt it would be difficult for municipal politicians to embrace a spring date for the siting process during an election year because of the fear of a negative backlash at the polls."
The mayors also "favoured a soft or low-key launch" of the search process, according to the Ontario Power Generation notes.
The waste authority launched its search nationally in May 2010, but Cheryl Grace, with the two activist groups, said county residents were kept in the dark.
"The first time Bruce County residents heard anything about a Bruce County municipality actually being involved in any of this in a tangible way was October 2011," Grace said from Southampton.
Brockton Coun. Chris Peabody also expressed concern.
"They're not supposed to meet as a group in secret," Peabody said from Walkerton.
"It's very concerning that over such a very important issue that the Nuclear Waste Management Organization and the Bruce county council appear to have contravened the Municipal Act."
Bagnato said there was nothing "sneaky" going on.
The 15- to 20-year process of finding and constructing a site in Canada to store the waste had to start somewhere, he said.
"They were just trying to put their ducks in a row to introduce it," Bagnato said.
"It wasn't like we're going to secretly have high-level waste here shortly and you'd better keep it a secret from the public."
Bagnato did admit he didn't want to be "knocking on doors about high-level nuclear waste" during the 2010 election, which he lost anyway.
Mike Smith, mayor of Saugeen Shores and former county warden, said the meetings were simply briefings at which they passed no motions.
He disagreed with the activists' complaints of secrecy.
"That's their interpretation of things," Smith said from Southampton, near the Bruce nuclear power plant on Lake Huron.
"This information was public on websites and everywhere."
Michael Krizanc, spokesman for the Nuclear Waste Management Organization, could not immediately be reached for comment.
But he told the Walkerton Herald-Times the agency was open about what it was doing, and how and when the mayors communicated with their communities was up to them.
If the groups are not happy with how the county handles their complaint, they plan to take their case up with the province's attorney general and minister of municipal affairs.