Former Liberal leader John Hewson has described the upcoming Wentworth by-election as a "unique opportunity to register a protest vote".
Dr Hewson, who held Wentworth from 1987 to 1995, has urged voters in the blue ribbon Liberal seat vacated by Malcolm Turnbull to send a message to the government over its inaction on climate change by voting for an independent.
They can change their vote later at the general election, he said.
"The by-election should be a referendum on climate policy," the former federal opposition leader told AAP.
Although Dr Hewson has not officially endorsed any of the candidates, he directed praise towards independent Kerryn Phelps, saying she had been focused on addressing climate change.
