The former director of the Victorian Liberal Party, Damien Mantach, stole more than $1.5 million from party coffers partly in an attempt to save his marriage, a court has heard.

Mantach, 42, has formally pleaded guilty in the Victorian County Court to 15 charges of obtaining financial advantage by deception relating to a complex scheme of issuing fake invoices.

He issued 53 bogus invoices starting in the months before he was appointed director in early 2011 until his resignation in March 2015.

Mantach spent the majority of the money on shares and the purchase of a cafe in his home town of Ocean Grove.

His defence lawyer Geoffrey Steward said Mantach and his wife Jodie had been suffering marital problems for several years and that he had bought the cafe for her.

Judge Liz Gaynor told the court she accepted the money had not been spent on buying "Ferraris and boats".

"It's clear his marriage was in strife and this was his simplistic way of dealing with it," she said.

The court heard Mantach had made full admissions and explained to police how he orchestrated the fraud scheme at the earliest stage of their investigations.

Mr Steward said Mantach had expressed an immeasurable degree of remorse and had taken the blame entirely.

"This is a fellow who was rubbing shoulders with Prime Ministers and Premiers and now he's sharing metaphorical porridge with prisoners," he said.

Judge Gaynor noted Mantach had been "unusually remorseful, co-operative and remorseful" but said a prison term would be appropriate.

He will be sentenced next month.