Facing Victoria's Electoral Matters Committee on Friday, the renowned psephologist and ABC election analyst said the system distorted voters' will.
Mr Green called for group voting tickets to be dumped and noted Victoria was the only Australian jurisdiction still using the system, which allows parties to distribute upper-house preferences when people vote above the line.
"Voters have trouble finding the candidates they know amongst the flotsam and jetsam that washes up on the ballot paper for the purposes of manipulating preferences," he told the committee.
"If you abolish group voting tickets, you will shrink the size of the ballot paper, have fewer parties nominating and (that will) result in more candidates being elected in proportion to their votes."
Manipulation of the voting system was laid bare before last year's state election after so-called preference whisperer Glenn Druery was covertly recorded boasting about his method.
In the footage, Mr Druery asked representatives from the Angry Victorians Party to pay $55,000 for each candidate he managed to get elected through his backroom dealings.
Mr Green recommended Victoria adopt a simple "one above the line" voting system.
Group voting tickets allow Labor and the Greens, who compete in most regions for a seat, to talk to other parties in the hopes of attracting preferences, Mr Green said.
"Some of this comes down to political interest of parties," he said.
"I'm more interested in the fact then when people turn up to vote, members elected should reflect their votes."
As it stands, at least one and sometimes two members are elected to each of the eight upper house regions because of political deals, Mr Green said.
Animal Justice MP Georgie Purcell was elected to the Northern Victoria region last year after receiving 1.53 per cent of the primary vote.
The Victorian Greens, describing group voting tickets as undemocratic, have lobbied for the system to be done away with in time for the 2026 election.
Appearing before the inquiry on Thursday, outgoing Labor state secretary Chris Ford indicated the party's in-principle support for abolishing group voting tickets.
But the change should be in conjunction with broader upper house reform, Mr Ford suggested.
Opposition Leader John Pesutto said the Liberal party also supports scrapping the system.
Mr Green also said the Victorian Electoral Commission was suffering from an outdated election management system, with too many pre-poll votes counted at a central activity centre.
He argued the state needs more counting centres.
"Other states have a central activity centre, but they only deal with declaration votes," Mr Green said.
"It's only in Victoria that they deal with ordinary votes as well because of the way pre-polls are taken."
The electoral matters committee is examining how the 2022 Victorian state election was conducted.