Labor has claimed victory in the formerly safe Liberal seat of Hawthorn, defeating Liberal leadership aspirant John Pesutto.

Key points: Sam Hibbins has retained the seat of Prahran, which he first won in 2014.

Sam Hibbins has retained the seat of Prahran, which he first won in 2014. The Liberal candidate, Katie Allen, won the most first-preference votes but was overtaken on preferences

The Liberal candidate, Katie Allen, won the most first-preference votes but was overtaken on preferences Independent Ali Cupper has won the formerly safe Nationals seat of Mildura

Mr Pesutto first learned he was in trouble in his seat in Melbourne's inner east on live television as he appeared on ABC TV's election night broadcast.

The seat has not been held by Labor since 1955, and the Shadow Attorney-General went into the campaign with an 8. 6 per cent margin.

But at 5:00pm on Tuesday, Labor candidate John Kennedy was 173 votes in front of Mr Pesutto.

Mr Kennedy took to Twitter to claim victory and thank his supporters.

"My promise is to work hard every day to repay the faith put in me," Mr Kennedy said.

"I wish John Pesutto all the very best for the future," he said.

Mr Pesutto is yet to concede defeat.

He was a frontrunner to take over the Liberal leadership after Matthew Guy stepped down.

Shadow Treasurer Michael O'Brien is expected to be a candidate when the party elects its new leader on Thursday.

Sam Hibbins faced a challenge from both Labor and the Liberals. ( Twitter: Sam Hibbins )

Earlier, the Victorian Greens claimed victory in the seat of Prahran, maintaining their hold on three seats in the Lower House.



Greens MP for Prahran Sam Hibbins will join Ellen Sandell (Melbourne) and Tim Read (Brunswick) to maintain the Greens' presence in the Lower House.

Mr Hibbins thanked the voters of Prahran for giving him the privilege of a second parliamentary term, and applauded his fellow candidates for running strong campaigns.

"The Greens stood on a positive, progressive platform of better public transport, affordable housing, clean energy and protecting our environment," Mr Hibbins posted on Facebook.

"As promised, my first priority will be to re-introduce the Greens' bill to protect LGBTIQ students from discrimination."

Mr Hibbins first won the seat for the Greens in 2014 by defeating the sitting Liberal MP Clem Newton-Brown.

Prahran was Victoria's most marginal seat going into the 2018 poll, with a margin of only 0.4 per cent.

This election, the fight for the seat in Melbourne's inner-south, was a three-way contest between Mr Hibbins, Labor candidate Neil Pharaoh and Liberal Party candidate Katie Allen.

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Dr Allen received the most first-preference votes, followed by Mr Pharaoh and Mr Hibbins, but once preferences were distributed, the Greens MP was 5,845 votes ahead of his Liberal opponent.

Reacting to the result on Twitter, Dr Allen questioned whether a rethink of the preferential voting system was required, but later tweeted that she had been joking.

Mr Pharaoh conceded defeat on Tuesday afternoon.

"Unfortunately Labor hasn't won Prahran," Mr Pharaoh tweeted.

"The preferences didn't flow our way. We gave it all we had, and I'm so proud of everyone who was part of our campaign."

Independent Ali Cupper will be a new addition to the crossbench. ( Facebook: Ali Cupper )

Meanwhile, independent Ali Cupper has claimed victory in the formerly safe Nationals seat of Mildura in the state's north-west.

The seat had been held by Nationals MP Peter Crisp on a margin of 8 per cent.

Ms Cupper will join the independent MP for Shepparton, Suzanna Sheed, on the crossbench of Victoria's Lower House.

The Greens win in Prahran gives the party three seats in Victoria's Lower House, the same number the party held going into the election.

Before the election, the party had hoped to hold the balance of power and take a ministry in a minority Labor Government, but Labor's crushing victory ruled out that prospect.

Lidia Thorpe won Northcote at a 2017 by-election, then lost it a year later. ( AAP: Mal Fairclough )

The Greens gained the seat of Northcote in a by-election last year but lost it to Labor in the general election, ousting the Victorian Parliament's first Aboriginal woman MP, Lidia Thorpe.

But that loss has been offset by its gain in Brunswick, while Greens MP Ellen Sandell retained the seat of Melbourne which she wrested from Labor in 2014.

The Greens were plagued by negative press surrounding a number of their candidates during the campaign, including one who was accused of serious sexual misconduct.

They also defended their candidate for Footscray, Angus McAlpine, after it was revealed he rapped about condoning date rape, drug use and domestic violence.

One of Ms Thorpe's staffers also attracted media criticism over a number of tweets he posted about pornography and sexual assault.

The party has suffered a big hit in the Upper House, where party leader Samantha Ratnam is its only remaining MP.

Samantha Dunn, Sue Pennicuik, Huong Truong and Nina Springle all appear likely to lose their seats, although counting in the Upper House has not been finalised.

The Greens blamed the losses on preference deals between the minor parties.