A big injection of GST money could stabilise WA’s credit rating.

Standard and Poor's (S&P) has kept Western Australia’s credit rating at AA+ (after downgrading the state from AAA in 2013), but says it still has some worries on the horizon.

The analysts say WA’s budget deficits will continue until a forecast increased GST revenue comes through, at which point it should return to small surpluses.

The state’s latest budget papers estimated GST revenue would rise from $2.035 billion in 2016-17 to $6 billion in 2019-20

Meanwhile, they state that deficits currently forecast to hit $3.9 billion will be temporary.

S&P says the state’s debt should remain “moderate”, despite weaker revenues.

But it warned the deficits could “persist and increase its debt burden should the Government fail to further constrain spending growth ... or should its revenue fall even further”.

“Should there be further revenue or spending slippage, the state's cash operating deficits could be more long-lasting than we currently expect, and the state's tax-supported debt level could also increase to above 120 per cent of operating revenues, absent mitigating actions,” the agency said.

“Meanwhile, we consider it could be challenging for the state to further achieve its cost savings targets.”