The South Australian Liberal Party is accused of "an outrageous abuse of taxpayers' money" after allegedly spending thousands of dollars on internal polling ahead of a tense by-election.
But the opposition has hit back, saying the spending was approved by the Treasury.
The Labor government says it has leaked information that strategist firm Freshwater was paid $25,905 to conduct research for the Liberals before Saturday's by-election in Black.
Freshwater was paid using the Global Allowance entitlement, the guidance of which excludes "election expenses, other than Postal Vote Applications".
Treasurer Stephen Mullighan said taxpayers were charged almost $40,000 for polling, public relations support and letters to constituents endorsing the Liberal candidate in the by-election.
"On the face of it, this is an outrageous abuse of taxpayers' money by the Liberal Party," he told reporters on Sunday.
Mr Mulligan also suggested that the invoice was for polling reported on by The Advertiser on October 10 which was used to "road-test" two local councillors as prospective candidate for the Black by-election.
"Clearly the Liberal Party concocted this scheme to avoid having to pay for the internal polling themselves," he said.
But the Liberals maintain the funding was approved by Treasury.
"The Treasurer's own department advised and approved this expenditure by David Speirs," state director Alexander Hyde told AAP.
"It is incredibly embarrassing for Stephen Mullighan that he doesn't even know what his own departmental staff are approving, or what his own guidelines allow."
Mr Hyde said the invoice was "entirely unrelated" to the polling done in October that was reported by The Advertiser.
Tensions are running high ahead of the Black by-election on Saturday which was prompted by former South Australian Liberal leader David Speirs quitting politics.
Mr Speirs resigned as opposition leader on August 8, declaring that he had "just had a gutful" of leadership speculation and did not have the energy to keep fighting.
He then resigned from parliament after being charged with supplying drugs following the emergence of footage purportedly showing him snorting white powder.
