Alberta separatists have delivered more than 300,000 signatures to elections officials in western Canada, in support of their attempt to force an independence referendum in Canada’s oil-rich province.

But the effort stumbled immediately as a separatist-linked group posted the personal data of nearly 3 million residents online in one of the largest data breaches in Canadian history, fomenting fears of a possible political interference crisis.

On Monday, hundreds of supporters gathered in Edmonton, the provincial capital, as Mitch Sylvestre, a separatist leader, delivered the petitions to Elections Alberta.

“We’re not like the rest of Canada,” Sylvestre told reporters and attenders. “We’re 100% conservative. We’re being ruled by Liberals who don’t think like us.”

A minority of residents of the oil-rich province have long argued that the province’s woes are due to the structure of payments to Canada’s federal government and a perceived inability to get their vast fossil fuel reserves to market. In recent months, separatists have seized on the sentiment. Polls put separatist support between 18% and 30%.

Last year, Alberta’s premier, Danielle Smith, reduced the number of signatures required for citizens to bring a constitutional referendum, dropping it from 588,000 to roughly 178,000. The provincial government also changed how citizen-initiated referendums worked, removing powers from Alberta’s chief electoral officer. Now, referendums can pose questions that would run afoul of the Canadian constitution.

They hope their question – “Do you agree that the Province of Alberta should cease to be part of Canada and become an independent state?” – will be added to a planned referendum in October, which will also include questions on immigration, healthcare and the country’s constitution.

While the separatists have cleared the required signatures needed for a separatist referendum, Elections Alberta says it needs to verify the names. But the process has been put on hold by a court ruling.

Indigenous nations in Alberta, whose treaties with Britain predate the creation of Alberta, say that a possible referendum vote on separating from Canada would violate their treaty rights.

“Alberta has treated [Sturgeon Lake Cree First Nation] as though they are chattel on the land, merely an afterthought in forced negotiations, not the first step in any potential secession,” the First Nation said in its court filing. “Alberta has no right to secede from Canada and no right to take Treaty No 8 territory.”

The First Nation has also warned the current push had invited the threat of influence of foreign actors and a vote to leave Canada “will enable foreign interference from the most powerful nation to the south”.

Late last year, separatist activists held covert meetings with members of Donald Trump’s administration.

The former Alberta deputy premier and pro-federalist Thomas Lukaszuk says the movement to secede from Canada is “a form of treason” and something “most of us Albertans and Canadians don’t stand for”.

But the revelation that a separatist-linked group obtained Alberta’s official list of electors – a database of the names, home addresses and contact information for roughly 2.9 million voters – has unleashed political chaos in the western province.

The list was provided to the Republican party of Alberta, which is legally registered, but was then improperly shared with the Centurion Project, a pro-separation group which allegedly used the list to target voters. A court ordered the database to be taken down, and both Elections Alberta and the RCMP launched investigations. But the data has probably been copied and shared already.

Among the names visible on the database were prominent politicians, elections officials, senators, judges, Crown prosecutors, journalists and other public figures.

Jared Wesley, a University of Alberta political scientist, wrote that a public inquiry is needed “before [Albertans] cast another ballot”.

He warned that Elections Alberta, by investigating itself, “is now defending its own response, its own mandate, and the integrity of the democratic system it administers”.

Separatist groups say they will cooperate with any investigation, but expect the government to proceed with a referendum.

“We expect our question to be on the ballot this October regardless of what the courts say, regardless of what Elections Alberta says,” Jeffrey Rath, one of the separatist leaders, told reporters.

He said getting the 300,000-plus Albertans signed up took immense effort. “All of our people were out busting their asses collecting signatures. Period.”