Victorian Premier Jacinta Allen is facing growing pressure over her leadership after new polling suggested Labor is on track for a heavy defeat at the November 28 state election.

The latest Herald Sun poll has the Coalition leading Labor 56-44 on a two-party preferred basis.

WATCH THE VIDEO ABOVE: Jacinta Allan faces leadership crisis as polls plummet

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On primary votes, the Coalition is on 29 per cent, while Labor has fallen behind One Nation, which is polling 24 per cent.

One union boss has warned of an “orange wave”, saying One Nation could win as many as 34 seats if the polling is replicated at the election.

Jacinta Allen faces potential leadership spill as Labor trails in polls Credit: 7NEWS

Speculation over Allen’s future intensified over the past 24 hours, with MPs and Labor powerbrokers reportedly counting numbers to determine whether there is enough support for a leadership spill.

Allen is facing mounting pressure over Big Build corruption allegations, cost of living pressures and this week’s teachers’ strikes.

Reports suggest a leadership spill could happen as soon as Tuesday when MPs return to state parliament.