The police fraud squad is investigating allegations former Victorian Liberal Party state director Damien Mantach embezzled around $1.5 million of election campaign funds.

The money is alleged to have vanished over four years to fund Mr Mantach's lifestyle.

An audit of the party's finances after last year's state election loss uncovered unauthorised financial transactions linked to Mr Mantach, with money missing from both state and federal campaign funds.

The Victoria Police fraud and extortion squad has been called in to investigate.

Liberal Party president Michael Kroger said Mr Mantach had admitted to wrongdoing.

"We feel profoundly betrayed and terribly disappointed with what's happened," Mr Kroger said.

Key points: Liberal Party accuses former state director of embezzling $1.5m

Liberal Party accuses former state director of embezzling $1.5m Alleged theft happened over four years

Alleged theft happened over four years Victoria Police fraud and extortion squad called in to investigate

Victoria Police fraud and extortion squad called in to investigate Party believes Mantach took the money to fund his lifestyle

He said the party believed Mr Mantach had acted alone.

"We're not aware that anyone at the party head office or any officials had any involvement at all," he said.

It also emerged that Mr Mantach repaid tens of thousands of dollars during his time as state director of the Tasmanian branch.

In a letter to members posted on Facebook, Tasmanian Liberal president Geoff Page said in March 2008 that when he left the role, Mr Mantach fully repaid a liability of nearly $48,000 for personal expenses.

Mr Page said the division considered the matter closed and had robust internal financial processes.

Mr Kroger said he did not believe the missing money influenced the 2014 election result, or that it would affect the next federal election.

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Liberal leader Matthew Guy said the party was furious at what he called a "pretty basic effort at embezzlement".

"We want our money back," he said.

"We want this matter sent to the police and we will be doing everything we can to ensure that justice is done.

"I saw someone making a comment that we're white hot with anger, that's just the start of it."

Mr Kroger said the missing money was confined to the party's Victorian division and he was confident some of it could be recovered through assets bought with the funds.

Mr Kroger conceded the Liberal Party had failed to properly monitor spending.

"Obviously it should have been picked up years ago — it wasn't," he said.

Former premier Denis Napthine, who led the party during last year's campaign, said he was surprised and bitterly disappointed by the allegations.

The party's administrative committee met this morning to discuss how to deal with the missing money.

Mr Mantach has been contacted for comment.