The Electoral Districts Boundaries Commission will next month begin a series of regional consultations as it considers submissions proposing the boundaries of various rural centres be dramatically changed.

In an update on its website, the commission says it is considering a number of changes that would impact on Liberal-held seats such as Stuart, Chaffey, Hammond and Finniss, including combining Port Augusta and Whyalla into a single district, and potentially removing or substantially recasting Geoff Brock’s seat of Frome.

Brock has not returned numerous calls from InDaily to discuss his seat.

The commission says the change could see “areas south of Port Pirie and west of the Mount Lofty Ranges, including Jamestown, Clare and Kapunda, be amalgamated to form a mid-north district”.

It also announced that it is “considering changes to the electorates of Chaffey and Hammond, to bring river towns such as Cadell, Morgan and Blanchetown into Chaffey and to move the south-western part of Chaffey into Hammond”.

“It was also suggested that a proposal to amalgamate the townships of Victor Harbor and Goolwa into one district was under consideration,” the commission wrote.

“That would then have flow-on effects in terms of the surrounding electoral districts.”

None of the MPs affected by the proposed changes was aware of them when contacted by InDaily.

Goolwa is currently part of Liberal Adrian Pederick’s seat of Hammond.

He told InDaily “you could look at (Goolwa and Victor) as like-minded communities but I’m not sure how you’d make the numbers work”.

“Over time there’s no doubt Hammond will get tighter and tighter as Murray Bridge grows,” he said.

“It’s going to become a lot more marginal… no doubt, over the next 20 years, it will slowly get tighter and tighter just on the numbers.”

He was unsure how the proposed changes would affect his margin but conceded “every time you compress farmland you’re essentially losing Liberal votes”.

Liberal MP for Finniss Michael Pengilly was uncertain there were enough people in Goolwa and Victor Harbor to justify a standalone seat, but conceded “eventually the south coast will be one seat”.

“But we’re a long way away from that… Victor, Port Elliot, Goolwa and Middleton will become one seat (over time) but that’s a fair way away,” he said.

Asked whether he would be recontesting Finniss in 2018, Pengilly said he was “not making any comment until the boundaries are redistributed”.

“The boundaries findings will determine what happens with a number of people on our side, and on the other side,” he said.

“It will possibly determine a number of members’ plans on whether they seek to recontest preselection and go on or not, that’s my view.”

The regional changes mooted are likely to be made on the basis of shifting population numbers, with Chaffey MP Tim Whetstone saying: “Sadly for me it tells the story that we have a declining population in Chaffey.”

“We’re still drought-affected, people are moving away… the only real way they’re going to put more people into the electorate is to encompass the more western towns of Cadell, Morgan and Blanchetown,” he said.

But the more radical changes – in terms of their potential electoral impact – would be to more marginal electorates in metropolitan Adelaide, with several under the microscope.

“In relation to the city, it was announced that consideration was being given to re-casting the currently elongated north-south coastal electorates, such as Lee, Colton, Morphett, Mitchell, Bright, Reynell and Kaurna to more regular shapes in an attempt to correct distortions which have occurred due to population expansion over time,” the commission stated on its site.

Any significant redrawing of the metropolitan boundaries would have the Labor Party concerned, given its dominance in metro marginals in recent elections – having won three of the last four polls despite having less than 50 per cent of the statewide vote.

Labor Party state secretary Reggie Martin would not comment on the proposed changes.