Federal Labor will ask the auditor-general to investigate the Liberal Party's Parakeelia "scam" as a matter of urgency.
Opposition Leader Bill Shorten likened the database provider to a "Liberal Party washing machine" turning taxpayer dollars into party profits.
The Greens already have asked the Australian Electoral Commission and the Department of Finance to conduct separate investigations.
Parakeelia is a wholly Liberal Party-owned firm registered to the same office building as the party's Canberra headquarters.
It provides voter monitoring software to coalition MPs, for which they pay $2500 a year, either from their own pockets or from a taxpayer-funded allowance for software.
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Parakeelia is the Liberal Party's second biggest donor, providing more than $1 million over the past three years.
Prime Minister Malcolm Turnbull says the company provides database services to Liberal Party members as does a similar Labor entity.
Mr Shorten said the community was becoming increasingly concerned taxpayer dollars were going into Liberal Party coffers.
The prime minister needed to say whether he approved or thought it improper and shut it down.
"Mr Turnbull needs to get off the ... fence and stop being in denial about the scam," he told reporters in Perth.
Liberal frontbencher Arthur Sinodinos said the party would fully co-operate with the Auditor-General.
"For the sake of transparency, maybe Labor should lay out their arrangements with the Auditor-General as well and then the public can have a full view about how these arrangements operate," he told Sky News.
