Mrs Mirabella yesterday brushed aside claims her camp was running scared at the groundswell of support for independent candidate Cathy McGowan, as the leaked email — sent by one of her key staffers and revealed by Crikey — circulated on the internet.

It came as journalist and Melbourne City councillor, Stephen Mayne, threw his support behind Ms McGowan and declared Indi the most likely seat in Victoria to fall from the hands of a major party.

A swing of 9 per cent is needed for Mrs Mirabella to lose the seat, which she has held since 2001.

The email, seen by The Border Mail, was sent by Mrs Mirabella’s media adviser Adam Wyldeck. It called on Liberal supporters to flood newspapers with letters.

Mr Wyldeck wrote it was “time to turn the tables” as Ms McGowan’s team had been sending “vitriolic letters of hatred towards Sophie as well as supportive letters about (Ms McGowan)” since the campaign began, and that “we are getting severely outflanked by a far more active and enthusiastic campaign team”.

“We have been thoroughly outgunned so far by the McGowan camp and it’s well and truly time to fight back,” the email read.

Mr Wyldeck even suggested topics to write about, such as “Sophie is strong, experienced and gets the job done”, questioning Cathy McGowan and where she stands, and questioning the impact of independents, especially if there is no hung Parliament.

Mrs Mirabella called Mr Wyldeck — who has been on staff for about three years — a “very enthusiastic young campaigner in the throes of an election campaign”.

She said she had “counselled” him — “I told him not to be so enthusiastic”.

Mrs Mirabella said she was “absolutely not” worried about losing Indi.

“I’ve got hundreds of supporters across the electorate,” she said.

“I’ll continue door-knocking and speaking with people on the issues that matter.”

Mr Mayne, on Twitter yesterday threw his support behind Ms McGowan. He said his attention had been drawn to Indi after outgoing independents Tony Windsor and Rob Oakeshott awarded Mrs Mirabella their unofficial “nasty prize” for MPs in the last Federal Parliament.

Mr Mayne has watched Mrs Mirabella rise within Liberal Party ranks since her days at Melbourne University and believes “politics can do without her disposition”.

“Indi has been neglected as it’s been a safe Liberal seat, but the smart thing for the people of Indi is to put forward a conservative independent,” he said.

Mr Mayne said he had had no contact with Ms McGowan, other than “a few tweets back and forth” and believed she was polling upwards of 20 per cent.

The Border Mail could not confirm this number last night.

Mr Mayne is the third high-profile figure outside the electorate to weigh in on matters in Indi.

Asked why the North East was getting such attention, he said Indi had emerged as the most likely seat in Victoria to go from a major party to an independent.

And that was “primarily about an individual who’s quite unpleasant”.

Mrs Mirabella said she was “not really concerned with what people in Melbourne have to say”.

Ms McGowan was surprised by yesterday’s happenings but said it showed people were responding to her “professional, grassroots campaign”.