High-profile shareholder activist and Crikey founder Stephen Mayne has announced he will run as an independent in the by-election for the state seat of Melbourne.

The by-election, to be held on July 21, was prompted by the resignation of long-serving Labor MP Bronwyn Pike.

Labor and the Greens have both announced City of Melbourne councillors as their candidates, but the Liberal Party is unlikely to contest the by-election.

Mr Mayne, who founded the alternative news website Crikey, says he will campaign on a "business-friendly" platform to provide a choice for Liberal Party voters.

"I think with 28 per cent of the Liberal vote looking for a home, then clearly there's a good chance of a Liberal-friendly independent getting into double figures," he said.

"Ultimately any preference decisions may well determine the seat."

Mr Mayne says he is unlikely to entertain any preference deal with Labor, but is open to a deal with the Greens.

"I'm still shaking my head at the HSU (Health Services Union) scandal and all the sleazy culture of the Labor Party and can't believe what the Labor Party did to Andrew Wilkie over poker machine reforms," he said.

"I think voters in the inner-city seat of Melbourne will also share many of those concerns."

Mr Mayne has campaigned unsuccessfully in the past for a seat in the Victorian Upper house, and also contested Peter Costello’s former seat in the Federal Parliament.

He is currently a member of the Manningham City Council in suburban Melbourne.

Greens candidate Cathy Oke has welcomed Mr Mayne's decision to contest the by-election.