Alberta's AAA credit rating will worsen under the NDP government's debt-heavy budget, says Moody's Investors Services.

On Wednesday, the New York-based bond credit rating agency said Alberta's "deep budgetary imbalances and heavy infrastructure investments will result in a deterioration in its credit metrics over the next 24 months" as the projected $47-billion in debt by 2019-18 "is high for an oil-dependent regional government, and surpasses Moody's previous expectations."

During question period on Wednesday, Wildrose Leader Brian Jean asked Premier Rachel Notley if the government was banking on an oilsands "superboom" in 2018 to achieve its balanced budget plan and dodge a downgraded credit rating.

"This budget is in shambles. If the NDP killed every dollar of infrastructure spending, they would still need to borrow to balance the books, but the budget's energy revenue projections are even crazier," he said.

"Moody says that the government may be overprojecting oil prices by as much as $20 a barrel."

Notley said the government is using "conservative" oil forecasts and has introduced legislation that would cap Alberta's debt to 15 per cent of nominal GDP, or roughly $55 billion.

"That puts us at one-half the average debt level of all the provinces in the rest of the country, so that is an exceptionally responsible, careful way forward. It's what these guys asked for a mere two days ago, but apparently it's not good enough."

Moody's expects Alberta's debt burden to increase to around 60% of revenues by 2016-17, rising to 80% by 2017-18.

matthew.dykstra@sunmedia.ca

@SunMattDykstra