Daniel Andrews has issued a blistering statement about the "smear and innuendo" surrounding an anti-corruption investigation.
The Victorian premier is facing questions about his role in awarding two grants worth $3.4 million to a Labor-linked union.
The money was promised to the union on the eve of the 2018 election despite objections from health department officials.
The grants are being investigated by the state's Independent Broad-based Anti-corruption Commission.
"Regardless of any smear, innuendo or media reporting based on anonymous sources, the only IBAC matters I will comment on are those that are the subject of a final report - as is appropriate and has always been my practice," Mr Andrews said in a statement on Saturday.
"Questions about what IBAC is or is not doing are a matter for the independent agency.
"I act appropriately at all times and in all things. That is the oath I swore and I take it very seriously."
Mr Andrews later batted away questions about the IBAC probe, telling reporters he had no further comments beyond his statement.
When asked whether Victorian voters should have faith in him, Mr Andrews said: "I would simply point to the fact that when we make promises, we keep them."
Liberal leader Matthew Guy said it is the fourth time the government has been investigated by the anti-corruption commission and "leopards don't change their spots".
"The only way we're going to get a government of integrity is to change the government," Mr Guy said on Saturday, adding that he would boost IBAC's funding if he was elected.
In a statement, the watchdog said the secret investigation did not meet its threshold to hold public hearings and it would be unfair to people involved if preliminary findings or other private information became public.
It has recommended the government introduce an offence for people who publish information contained in IBAC draft reports - a proposition Mr Andrews wouldn't rule out.
Mr Guy said he wouldn't pursue the legal change.
The comments come as a poll shows rising support for the coalition and a falling Labor vote, although the Andrews government retains an election-winning lead.
A Newspoll published by The Australian showed Labor's primary vote had fallen to 37 per cent, down four per cent from late August, and now equal to that for the coalition.
Its two-party lead over the coalition also shrank to a 54-46 per cent share.
If that result were replicated on November 26, the Andrews government would suffer a 3.3 per cent swing althugh it would still secure a third term in office.
But the party could be in danger of shedding up to 10 seats from its 12-seat notional majority after the redrawing of electoral boundaries.
More than a quarter of the 1007 Victorian voters surveyed were considering casting their ballot for minor parties or independents.
The premier's satisfaction rating fell three per cent to 51 per cent, while Mr Guy's satisfaction rating sat at 32 per cent.
The Victorian Greens on Saturday launched an election pitch to shut down two prisons by mid-next year and redirect the funding into early intervention and public housing.
The party produced Parliamentary Budget Office costings to show closing the Barwon and Loddon prisons would save the state $215 million over the next decade.
Labor pledged to put $4 million into establishing a new mental health training program for trade apprentices
Mr Guy promised up to one million Victorian children would receive vouchers worth up to $200 to go towards recreational activities under a coalition government.