Western Australian Premier Colin Barnett's grip on power has slumped just 15 months out from the state election, a poll out today shows.

The Newspoll, published in The Australian newspaper, shows the Labor Party has increased its primary vote from 33 to 42 per cent in the past six months.

Key points: Labor pulls ahead in Newspoll for first time since Barnett came to power in 2008.

Labor pulls ahead in Newspoll for first time since Barnett came to power in 2008. Ballooning deficit, economic slump to blame.

Ballooning deficit, economic slump to blame. Labor leads Coalition 53 to 47 per cent on two-party-preferred basis.

Labor now leads the Coalition 53 to 47 per cent on a two-party-preferred basis.

This could give Labor a two-party-preferred swing of 10 per cent, which would allow it to claim 10 seats and form Government.

It is the first time Labor has lead the Coalition since Mr Barnett came to power in 2008.

Veteran political analyst Peter Kennedy said the Coalition had only itself to blame for the slump in the poll.

"One of the problems for the Government has been the deteriorating budget position," he said.

"I think its reputation as an economic manager, or financial manager, is on the line and that's where Labor has been making inroads.

"The good result for Labor sets the battle lines for the rest of the year and Mr Barnett will have the job ahead of him to peg Labor back."

Cabinet reshuffle, financial management key to retaining power

The Government has battled a worsening budget position on the back of a plunging iron ore price.

Mr Barnett has campaigned for the state to secure a greater share of GST revenue in order to fill budgetary black holes.

The Mid Year Economic Financial Outlook released last month projected the Government's deficit would balloon to $3.1 billion by the end of the financial year.

This will eclipse the state budget estimate in May of $2.7 billion.

Mr Kennedy said the only good news for the Government was it still had time before Western Australia went to the polls in March next year.

"Still 15 months out from the next elections, so there's plenty of time for Mr Barnett to turn the ship around," he said.

"Remember he will have a reshuffle of the Cabinet very shortly, and that will be an important opportunity to get his team in place to face the election early next year.

"I think the reshuffle of the Cabinet and also the budgetary position will be crucial in deciding who wins next year."

Labor leader Mark McGowan has also increased his popularity among voters.

He leads Mr Barnett as preferred premier, 41 to 36 per cent.