Preference whisperer Glenn Druery brokers deal between Derryn Hinch and Labor

Controversial preference whisperer Glenn Druery has brokered a deal between Labor and Derryn Hinch's Justice Party in a bid to win or hold three key marginal seats in Victoria.

The preference deal will likely boost the chances of Justice Party candidates joining the former broadcaster in the Senate, however Labor has said it made no policy promises in exchange for the influential crossbencher's support.

Senator Penny Wong and Senator Derryn Hinch during debate on the ABCC bill in the Senate at Parliament House in 2016. Credit: Alex Ellinghausen

The major parties have been in fierce negotiations with smaller players ahead of the start of early voting on Monday, with a formal deal between the Coalition and mining magnate Clive Palmer to be announced this week.

Former Liberal MP Julia Banks, who is running as an independent against Health Minsiter Greg Hunt in the Mornington Peninsula seat of Flinders, is expected to preference Labor in a move that will give the party a chance of unseating the long-serving MP.

Labor’s deal with Senator Hinch will be made public on Monday when candidates start distributing their how-to-vote cards at pre-polling stations as the campaign enters its final three weeks.

In exchange for Justice Party’s preferences in the seats of Casey, Macnamara and Corangamite, Labor will encourage its voters to place Senator Hinch-aligned candidates second on the Senate ballot. A Labor source said the party had not made any policy promises to Senator Hinch.

“We recognise that [Derryn Hinch] has a high profile in Victoria and is much more open to negotiations than the Greens,” the source said.

Scott Morrison and Bill ShortenCredit: Dominic Lorrimer/Alex Ellinghausen

“He is much more pragmatic. And the preference [deal] is about taking votes from the right-wing column.”

Labor is hoping an alliance with a “pragmatic” Senator Hinch will boost its chances of passing controversial legislation, including changes to superannuation tax and industrial bargaining reforms, through the Senate.

A recent Australia Institute polling found that the “best case” scenario for a Coalition government would be to deal with at least two minor parties to pass its legislation, while the “best case” for Labor would be to rely on Centre Alliance from South Australia.

But Australia Institute director Ben Oquist said while the deal could be mutually beneficial, it would be highly unlikely to have a "substantial effect unless the contest was very tight".

"While preferences could help at the margin, the new voting regime for the Senate means they count a lot less," Mr Oquist said.

Senator Hinch said his party was more centrist than others headed by Fraser Anning, Cory Bernardi and Pauline Hanson.

"So I think, compared to those parties, it gives them a fairly good choice to preference us ahead," Senator Hinch said of Labor.

Mr Druery, a staffer for Senator Hinch, was involved in complex negotiations over preferences with a string of minor parties in the Victorian state election and the 2013 federal election.

Candidates require a quota to secure a seat in the upper house but those who fall short may win after gaining second preferences from others.

However, reforms to Senate voting passed in 2016 means backroom preference deals matter less than they once did. The new system requires voters to number at least six boxes above the line or at least 12 boxes below the line.