A new poll shows the Federal Government could face a 10 per cent swing against it in the upcoming by-election in the West Australian seat of Canning.

The by-election will be held next month, and was triggered by the death of popular local Liberal member Don Randall, who held the seat with a margin of almost 12 per cent.

But a Newspoll survey published in The Australian today has found there could be a 10 per cent swing against the Government, putting the seat at risk.

The by-election is widely seen as a litmus test for the Abbott Government.

Canning covers approximately 6,178 square kilometres in south-east metropolitan Perth, and includes some rural areas. ( Supplied: AEC )

Federal Government frontbencher Josh Frydenberg said he believed the Liberal Party would win the seat, but said it would be a tough contest.

The Liberal Party has nominated active SAS officer Captain Andrew Hastie as its preferred candidate for the seat.

Mr Frydenberg said Captain Hastie was a very strong candidate.

"I think he'll do a fantastic job," he said.

But Mr Frydenberg said even with a good candidate, the Liberals faced a tough fight on two fronts.

"Don Randall, the sitting member, had won five elections. He was deeply respected," he said.

"The governments always tend to have a swing against them in by-elections. Certainly, you know, and we're behind in the polls now which makes that increasingly difficult," Mr Frydenberg said.

"But I'm very confident that we will retain that seat because we have a very good candidate and we have some good policies to offer."

The Labor Party will select its candidate this weekend, with the current head of the WA Law Society Matt Keogh tipped as the likely contender.

Voters in Canning will go the polls on Saturday, September 19.

Jobs to be key issue at by-election: Labor

Labor has already begun to draw the battlelines for the contest with Federal Labor MP Jenny Macklin identifying jobs as the key by-election issue.

"The biggest issue in Western Australia right now is jobs," she said.

"We see unemployment going up. Youth unemployment going up. Under-employment going up.

"This is a very, very serious issue for Western Australians."

Ms Macklin said Labor would campaign hard on creating and protecting jobs in a state where the end of the mining boom has seen thousands of workers lose their positions in the mining sector.

But she conceded Labor faced an uphill fight.

"We think it will be a very difficult fight. We understand that history is against us," she said.

Shadow Treasurer Chris Bowen said a seat vacated by the death of a sitting member had not changed hand for almost 50 years.

"The average swing away from a party where a member has tragically passed away is very small," he said.

"I think it's about 2 per cent, so it will be very tough for the Labor Party in this by-election.

"The Barnett Government has mismanaged the West Australian economy and Tony Abbott has taken Western Australia for granted so we'll be running a very strong campaign, but the odds are clearly with the Liberal Party in this environment, where a member has tragically passed away."