A possible merging of Australia's second-largest federal electorate with another to make an even bigger electoral division has been described as "ridiculous" by one of the MPs involved.

The South Australian outback seat of Grey covers a massive area of nearly 905,000 square kilometres.

The Australian Electoral Commission has described the seat as stretching from the Western Australian, Northern Territory, Queensland and New South Wales borders to Marion Bay on the Yorke Peninsula and Eudunda in the south.

The main towns include Ceduna, Port Lincoln, Whyalla, Port Augusta, Roxby Downs, Coober Pedy, Port Pirie, Kadina, Maitland, Orroroo, Peterborough, Burra and Eudunda.

Mr Ramsey has been the federal member for Grey since 2007. ( Supplied: Rowan Ramsey/Facebook )

The commission is expected to announce on Thursday whether South Australia will lose one of its 11 federal seats, as predicted by a Parliamentary Library report.

If that happens and there is not enough time for a redistribution before the next election, a "mini distribution" could result in a merger of Grey with the seat of Barker, which covers the south-east of the state.

Grey MP Rowan Ramsey said such a move would affect 98 per cent of the state.

"If we do fall to 10, which seems likely ... I understand the two seats with the smallest populations would be put together - and in this case that's Grey and Barker," he said.

"I jokingly said to someone I'd be the Member for Graker - that sounds pretty ugly and the result would be pretty ugly.

"It seems like April Fools Day - I mean it would be ... a ridiculous patch from Mt Gambier to Ernabella," he said.

Mount Gambier is halfway between Adelaide and Melbourne, while Ernabella (now known as Pukatja) is approximately 30 kilometres south of the Northern Territory border.

The distance by road between the two centres is 1,802 kilometres.

Mr Ramsey's electorate includes SA's vast APY Aboriginal lands. ( Australian Story: Kent Gordon )

Member for Barker, Tony Pasin, said he thought the merger possibility was "very, very unlikely" because any redistribution would be completed before the next federal election.

"The only way Barker and Grey would merge is if there is a situation where there is one seat to be lost - that's likely - and the redistribution hasn't occurred by the time of the next election - that's very unlikely," Mr Pasin said.

"I think [the redistribution process] is nine to 12 months and I can't imagine a circumstance, or at least it is very unlikely, that we will have a federal election within that timeframe."

He said the task of representing the hypothetically merged electorates would be "simply impossible".

"It would be close to 1 million square kilometres, it would mean the person representing the people living at Port MacDonnell is also responsible for the people living in Ceduna and the APY Lands," he said.

"There just isn't enough of anyone to go around."

The electoral commission said any re-distribution was quite an involved process with a number of public input periods.