Alberta Finance Minister Ted Morton expects the Sustainability Fund to shrink to $3 billion before the province's books are back in the black. (CBC)Alberta Finance Minister Ted Morton says he wants legislation in place to see the Sustainability Fund is replenished as soon as possible.

The province dipped deeply into the multibillion-dollar fund in its 2010-11 budget.

"I want to make sure that we have a legislated rule in place to make sure that fund gets built back up," said Ted Morton during a meeting with a CBC editorial board Thursday.

"Because there will be — no questions asked, somewhere in this next decade — another oil and gas recession."

The rainy day fund — estimated at $15 billion at the end of 2009-10 — has proven critical during the current downturn, Morton said, ensuring that while there could be "three or four" annual deficits, no long-term debt is being built up.

The Sustainability Fund is expected to end the 2010-11 fiscal year at $8.6 billion, and shrink to less than $3 billion before balanced budgets can be restored.

"When we get back in the black, we need to replenish or rebuild the Sustainability Fund, and we anticipate being in a positive cash balance — back in the black — in three years," Morton said.

There is no formula established yet as to how to rebuild the fund, Morton said, suggesting it could be a percentage of surpluses or a percentage of energy revenues. But he insisted legislation is needed.

"If you have a statutory rule, you can't change it without all Albertans knowing," he said. "And I think Albertans expect us to rebuild the Sustainability Fund."