Opposition Leader Jess Wilson will give notice to state parliament's lower house on Thursday that the coalition plans to move a motion of no confidence in the premier and her ministers.
Only one motion of no confidence can be moved each four-year term and can lead to the dissolution of parliament if passed, well before the scheduled state election on November 28.
Ms Wilson said there must be accountability for government failings, citing record crime, skyrocketing net debt, major project cost blowouts and delays, and the 2026 Commonwealth Games fiasco.
"Victoria needs a fresh start and that begins with changing the government and changing the premier," the state Liberal leader said.
"It's time for a new government with the right priorities and a clear plan to deliver for Victorians."
The earliest the motion can be debated and voted on under the terms of Victoria's constitution act is July 28, when state parliament returns following a six-week break.
The bid to oust Ms Allan is doomed to fail, with Labor holding an overwhelming majority in the lower house.
It has been almost six years since a no-confidence vote to oust Daniel Andrews as premier during Melbourne's second COVID lockdown was defeated 44-23.
Ms Allan has faced internal pressure over Labor's tanking poll numbers, but a speculated leadership challenge did not eventuate when the party caucus met on Tuesday.
Momentum ground to a halt after Ms Allan's main internal rival, Deputy Premier Ben Carroll, ruled out a challenge on Monday.
Tuesday's meeting was considered the last chance for at least six weeks for representatives to roll their leader, unless a special meeting was called over the mid-winter break.
Nine newspapers' latest Victorian Resolve surveys this week showed primary support for Labor falling to 26 per cent, level with Ms Wilson's coalition.
Support for One Nation was up three percentage points to 24 per cent.
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