Daniel Andrews has issued a blistering statement about "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 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 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."
In a statement, the watchdog said the secret investigation did not meet its thresholds to hold public hearings and it would be unfair to people involved if preliminary findings or other private information became public.
The election race is tightening three weeks out from polling day, with Labor in danger of slipping into minority government.
A Newspoll published by The Australian shows Labor's primary vote has fallen to 37 per cent, down four per cent from late August, and now equal to the coalition.
Its two-party lead over the coalition has also shrunk, with Labor ahead by 54 to 46 per cent.
If that result was replicated on November 26, the Andrews government would suffer a 3.3 per cent swing but still secure a third term in office.
But it could put the party in jeopardy of shedding up to 10 seats, with the government holding a 12-seat notional majority after electoral boundaries were redrawn last year.
More than a quarter (26 per cent) of the 1007 Victorian voters surveyed were considering casting their ballot for minor parties or independents.
The premier's satisfaction rating has fallen three per cent to 51 per cent, while Liberal leader Matthew Guy's satisfaction rating sits at 32 per cent.
Asked who would make a better premier, Mr Andrews still came up trumps with voters on 52 per cent with Mr Guy on 33 per cent.
The Victorian Greens have launched an election pitch to shut down two prisons and redirect the funding into early intervention and public housing.
The party has produced Parliamentary Budget Office costings to show closing the Barwon and Loddon prisons would save the state $215 million over the next decade.
The Greens want both jails shuttered by mid next year, with maximum-security prisoners transferred to the Chisholm Road Prison and medium-security inmates offloaded elsewhere.
Three in four staff would be redeployed and the remaining 25 per cent offered redundancy packages.
The Greens also want to scrap $300 million set aside for additional police recruitment, raise the age of criminal responsibility to 14, and overhaul bail laws.