The campaign for the December 6 by-election to replace the late Bob Such in Fisher has started with Labor candidate and anti-violence campaigner Natalie Cook hitting the airwaves today.

Cook and her husband Neil, whose 17-year-old son Sam Davis died in 2008 after being punched at a party, started the Sammy D Foundation to raise awareness of harm-causing behaviour and reduce youth crime.

After her candidacy for the seat was announced this week, Sammy D Foundation chairman Brett Duncanson wrote to supporters to advise “that as of today, Nat Cook has taken a leave of absence from her position as Executive Director as she contests the South Australian seat of Fisher.

“During this time for the Sammy D Foundation, it will be business as usual.

“Neil Davis will continue in his position as Executive Director, a role he shared with Nat, while we have just released our five-year strategic plan.”

Nat Cook, meanwhile, was on radio station FIVEaa explaining why she had joined the ALP to stand for Fisher.

“I have always been a person who has a strong social conscience; this is nothing new,” she told the station’s breakfast program.

“It should be no surprise to anybody where my allegiance would lie.

“I haven’t spent a long time thinking about this; I was actually hoping that my local member Bob Such would recover as he’s done such a great job.”

Cook said she met Bob Such several times, most recently when she addressed members of a parliamentary sub-committee.

“Bob was most supportive – he was a compassionate man.”

When asked if she was ready for the hurley-burley of state politics, Cook referred to the pain of losing her son in 2008.

“It’s the worst thing that can happen in the world; so someone having a go at me, well bring it on.”

The state Liberal Party will announce its candidate on Saturday after branch members meet to consider candidates.

Labor’s plans for the seat previously centred on a strong independent being carried across the line by Labor preferences. That equation has been inverted: it now it believes it has a genuine chance at winning the seat with support from independents and minor candidates.

The date of the by-election in the other vacant state seat – Davenport – continues to cause controversy.

Labor Speaker Michael Atkinson says he won’t allow the by-elections to be held on the same day, which is the preference of the state’s Electoral Commissioner and the Liberal Opposition.

Atkinson said on Tuesday the decision was inherently political because one by-election was sparked by a death, and the other was sparked by the “unnecessary” resignation of Liberal stalwart Iain Evans.

“Mr Evans was re-elected as recently as March … and is leaving parliament simply because his party didn’t form government,” he told ABC radio.

“He’s walking away and creating an unnecessary by-election.”

There was also no significant cost benefit in holding the by-elections together, Mr Atkinson said.

Iain Evans said it was “patent nonsense” to hold the polls separately.

“If the independent Electoral Commissioner wants them on the same day, surely common-sense says you should have them on the same day,” he said.

The Davenport MP defended his decision to resign just seven months after the state election, saying he had served in parliament for 21 years and it was time for renewal within the party.

The Australian reported today that the electoral commissioner will now write to the Speaker “urging him to put voters above party politics and hold two upcoming by-elections on the same day”.

Kay Mousley told The Australian she would write to Atkinson to object to his “political” decision to hold one by-election on December 6 and the other early next year.

She said she has had to write after he ignored her calls to his ­office on Monday.

“It would make operational sense to hold both by-elections on the same day,” she said.

“There is not a great cost difference, but from an operational perspective there are advantages, as in we don’t have to repeat the same process within a couple of weeks of each other.

“And also for the electors, because the boundaries are contiguous, it means they can then vote outside the district. I think there are benefits to the electors as well, so from those perspectives my preferred position is to hold them on the same day.”