A major Canadian oil and gas exploration company is shifting its entire 1981 exploration budget to the United States, in response to the recent Canadian federal budget. The budget restricts oil and gas price increases and applies a tax to all natural gas sales.

Canadian Hunter Exploration Ltd. of Calgary, the discoverer of the prolific Elmworth gas field will shift its exploration activity, budgeted at $50 million to $100 million to U.S. properties. John Masters, president, says much of this was to have been spent in Canada but that the decision to shift activity to the United States is a direct result of the budget.

Canadian Hunter is a privately owned company founded by Masters and James Gray, the company's executive vice president, in 1973. A major investor in the company is Noranda Mines, a Toronto-based diversified mining giant.

Masters says the Canadian government tells the oil and gas industry that its energy package is intended to encourage Canadian companies to acquire operations of foreign-controlled corporations. Hunter says people in Calgary are trying to figure out who has been hurt most by the budget and trying to buy them out. "It's like the Nazis sending Brown Shirts out to break the windows for the looters," he said.

Canadian Hunter had 20 drill rigs in operation in Elmworth until recently and was examining a number of projects in Canada. But, Masters says, it already is exploring in Texas, Ohio and Wyoming and plans to be involved in all U.S. exploration areas by the end of the next year.

Masters says the budget and energy package proposed last month cut one-third of the value of his company and personal assets.