Days after Spring Street was rocked by news that former Liberal state director Damien Mantach had siphoned at least $1.5 million from the Victorian branch, Mr Guy has privately told his party it had to move on – without embarking on a witch hunt to single out who was most responsible.

The Opposition Leader made his comments during an often heated three-hour crisis meeting with the rank-and-file at Liberal Party headquarters on Friday night, where tensions flared over the fact that Mr Mantach was able to spend four years embezzling money for his personal use without anyone noticing.

And by Saturday, the financial scandal had deepened, with political donors expressing anger at the Liberals' handling of the issue, and some senior figures calling on party elder David Kemp – who was president at the time Mr Mantach was hired by the Victorian branch – to provide an explanation of the recruitment process.

Former Victorian senator Judith Troeth asked for the "please explain" after it emerged that the Victorian Liberals did not appear to do rigorous background checks on Mr Mantach, and therefore did not know he was effectively sacked as a Liberal Party director in Tasmania over personal spending on his credit card.

"Dr Kemp owes it to all Liberal members and supporters to explain how such a serious mistake could have been made," said Ms Troeth, who was vice-president of the party between 1989 and 1992.

Meanwhile, a Melbourne businessman who donated $20,000 during Mr Mantach's tenure told The Sunday Age he was frustrated at the controversy and the party's silence towards members and donors.

"I'm incredibly disappointed to see this kind of scandal happen, which is something we've come to expect from Labor with its relationship to the unions and people like Kathy Jackson," he said. "It just goes to show all political parties are as bad as each other."

The Sunday Age can also report:

• Police are investigating allegations that Mr Mantach first began siphoning money as a deputy director ahead of the state election in November 2010, with the Liberals' executive told of at least two invoices that were lodged for alleged "kickbacks" external to the party.
• Victorian president Michael Kroger is understood to have informed members at Friday's state assembly that it was appalling Mr Mantach's actions could have gone undetected for so long, and strongly implied that the buck stops with the governing administrative committee.
• Tensions flared during the meeting, with former federal Liberal MP Julian McGauran angrily rejecting Mr Guy's view that the party should not find someone to blame for the financial scandal.
• The Liberal Party is considering a range of internal financial reforms, including the establishment of an audit committee comprising former senior party figures.

Suspicions around financial irregularities in the Victorian branch emerged a few years ago, when the financial committee became aware of an over-spend during the 2013 federal election. However, it was not until earlier this year, following an intensive forensic audit, that the party realised the problem was much worse, and linked to its former director.

Money illegally flowed through false invoices to a business called Campaign Mail Logistics, which was set up in May 2010 in the name of Mr Mantach's wife Jodie, registered at the family's home address in Ocean Grove a few month's before his first alleged misappropriation in November that year.

Mr Mantach has continued to keep a low profile since the news broke, and when contacted by The Sunday Age on Saturday, simply replied "no comment" before hanging up.