Queensland councils are concerned proposed local government election spending caps could allow third parties "with aligned interests" to distort polls.
In a new discussion paper, the state Labor government has proposed spending caps for mayors, candidates and third parties for all council elections in Queensland.
Mayoral candidate spending would be capped between $30,000 and $250,000 depending on their number of constituents, while candidate spending would be capped between $15,000 and $30,000.
Registered third parties such as unions or companies would be allowed to spend up to $3.8 million, either across all state LGAs or in just a single LGA.
The Liberal National Party has branded the proposed caps as a "financial gerrymander" which would allow third parties such as unions to spend up to 126 times more than some mayoral candidates during elections.
The Local Government Association of Queensland, which is the peak council body, has also expressed concerns.
LGAQ chief executive Allison Smith says elections should be fair, democratic and free from undue influence.
She says any changes to campaign spending rules should create an opening for unfair distortion by third parties.
"Councils across Queensland have called for any new campaign spending cap regime to be accompanied by new laws to prevent the potential distorting influence of any proposed spending caps by third parties with aligned interests," Ms Smith told AAP in a statement.
"We urge the government to ensure any proposed changes reflect this intent."
Brisbane Lord Mayor Adrian Schrinner, who's a Liberal National Party member, slammed the discussion paper proposals as a Labor plan to oust him.
He said the caps would allow the 26 registered unions aligned to the Labor Party to each spend $3.8 million at the upcoming Brisbane City Council election.
"We know in terms of all of the registered third parties, unions make up the vast majority of and and certainly other registered third parties are not particularly interested in local governments, unions are" Cr Schrinner told reporters.
"Unions are interested in Brisbane City Council, we have at least 12 unions that are active in the Brisbane City Council workforce, and so you know, do the math."
LNP integrity spokeswoman Fiona Simpson called the discussion paper "a brutal assault on democracy" and accused the state government of planning "blatant election rigging".
"In short, every other political party or independent candidate will be forced to fight for their beliefs with one hand tied behind their back, while the Labor Party and the unions will be allowed to play by their own rules," she said in a statement.
Deputy Premier Steven Miles said the proposed caps were similar to state election rules, and were higher than the amount most candidates spent on average in past elections.
He also insisted no decision had been made on spending caps, but the discussion paper was the start of a consultation process seeking feedback.
"Feedback, including from the LNP and Lord Mayor, will be considered in determining what caps the government ultimately proposes," Mr Miles told AAP in a statement.
