Damien Mantach defrauded the Victorian Liberal Party of $1.55 million while he was state director, and used some of the money to try to salvage a disintegrating marriage, a court has heard.

Mantach, 42, fronted the County Court on Friday to formally plead guilty to 15 representative charges of obtaining a financial advantage by deception, related to pocketing 53 payments from Liberal coffers between May 2010 and January last year.

Former Victorian Liberal state director Damien Mantach.

Judge Liz Gaynor was told Mantach and wife Jodie were enduring a marital breakdown at the time of the offending, and that the frauds - which Mantach used to buy a $611,000 cafe for his wife to run as well as shares, a car, and repayments on their Ocean Grove home - were his way of trying to address the problem.

"It was clearly a marriage that was in strife and this was his very simplistic way of dealing with it," Judge Gaynor said.