Prentice was one of the first to sound the alarm last fall that the Harper government's decision to hang out a not-welcome sign to state-owned enterprises would be a disaster for foreign investment in Canada's oilpatch.
The latest data suggest the situation hasn't changed much since he issued the alarm in a speech in London more than two months ago, Prentice said in an interview.
While he is careful to avoid attacking the government he once represented — and which some believe he one day aspires to lead — Prentice makes clear that the "tone" is proving an impediment to energy-sector expansion.
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Aside from stalling for months before approving the takeover of two Alberta energy firms in 2012 — Nexen Inc. and Progress Energy — by Chinese and Malaysian state interests, Ottawa has of late halted the acquisition of MTS Allstream.
The government has also signalled it would not stand idly by if a Chinese firm were to show an interest in BlackBerry, the troubled smartphone maker. The messages and actions, say critics, have chased away foreign suitors.
Last month, Prime Minister Stephen Harper compounded the problem by saying Ottawa needs wiggle room to decide on individual cases and that it would be "foolish to provide absolute clarity" about the rules.
Prentice agrees flexibility is useful, but also that the government needs to make clear it wants foreign investment — including from state-owned enterprises.
"Of the top 50 energy companies in the world, a large number are state-owned enterprises. My position has been that we want them to invest in Canada and we want them to platform multinational operations in Canada rather than in Houston or London," he said.
"I think we need to assure people that Canada is open for business and that we welcome foreign direct investment and that we can only achieve our ambitions with foreign investment because we don't have enough capital domestically... it's a tone we need to make clear internationally."
That is also the view of John Manley, the head of the Canadian Council of Chief Executives, who said the situation has reached the point where "the outcomes are too uncertain" for foreign companies that may want to invest in Canada.
"Companies are therefore reluctant to go to the effort and expense of trying to make an acquisition when they don't have a clear line of sight of what the outcome will be," Manley said.
Prentice's latest numbers show a precipitous drop-off in foreign investment in the energy sector since the new rules over state-owned enterprises were announced at the end of 2012, although he concedes there are other reasons for the decline.
Direct foreign investment as of December this year totalled $2.3 billion, compared with $29.2 billion for the same period last year. Mergers and acquisitions have fallen to $13.7 billion from $73.8 billion last year.
The issue is top of mind with Alberta Finance Minister Doug Horner, who said in an interview he intends to bring it up at the upcoming federal-provincial finance ministers meetings in the nation's capital on Sunday night and Monday.
"The issue is clarity," Horner said.
"When business does not have clarity, it does not move. That's what we are having now, we have this freeze, and it's because we do not have clarity."
Horner said even though the new restrictions were specifically aimed at state-owned enterprises, private sector firms have also felt the chill.
After a "challenging 2013," Prentice said he is hopeful 2014 will be a better year for the oilpatch — not just on investment, but also in dealing with the long-term problem of bottlenecks due to a lack of pipeline capacity.
That is essential for expansion of the oilsands, as well as to get producers better prices for their product.
The rapid expansion of transport by rail has eased some of the pressure, but Prentice said he is growing more hopeful of approval for a pipeline to the West Coast to ship Alberta bitumen to markets in Asia.
"I have called for some time for the government to appoint a representative to meet with the First Nations and that has happened, that report was released about a week ago. I think it's had a calming effect ... there's a dialogue starting," he said.
"It's a great opportunity for us. Canada is an Asia-Pacific country and assuming we can sort out our access issues, we have the capacity to be the dominant supplier into that marketplace, which from a geo-political or economic point of view is of extreme importance to Canada."