Each evening, when Canadians settle to watch television, they set a pattern perhaps unequaled in any other country. They systematically chose foreign programs-over whelmingly from the United States-over those produced in their own country.

Ever since the advent of television, Canadian politicians and intellectuals have bemoaned this pattern.

Now, according to a new study, the pattern is becoming even more pronounced as U.S. stations and U.S. programs shown by Canadian networks and cable systems are grabbing an increasing proportion of prime-time viewing here.

The latest criticism of what is happening to Canadian television comes from the Canadian Radio-Television and Telecommunications Commission, the government body designed to regulate broadcasting policy.

In a somber overview of Canadian television, the commission noted that 70 percent of all English-language programming in prime time was of foreign origin.

"It is undeniable that canadian viewers predominantly watch programming in the entertainment category and the origin of the programming seems to be of little or no significance to the viewer ... This progrmming is overwhelmingly of U.S. origin," the commission concluded.

in french Canada, U.S. programming has not penetrated the viewing audience as it has in English-speaking Canada. But even on the French-speaking networks, U.S. programming captures 25 to 35 percent of the viewing audience.

Despite a requirement that networks allocate half their prime-time slots for Canadian programs, the Canadian shows gradually have been pushed to the fringes.

economics and the strong American influence on many aspects of Candian cultural life help explain the viewing pattern.

Canadian networks, including the publicly owned Canadian Broadcasting Corp., find it cheaper to buy prepackaged U.S. programs than to produce programs in Canada.

The CBC has been more determined to resist the importation of U.S. shows than the private and regional networks, but even the CBC has yielded to the temptation of filling some of its prime-time slots with the most popular U.S. shows.

Last year, CBC executives unveiled a long-term plan to upgrade Canadian programming and to reduce U.S. influence. But the Canadian government announced $2 billion in expenditure cuts last fall, and the CBC's budget for next year was frozen at its current level.

The rapid expansion of cable to television-Canada has the highest per capital cable penetration in the industrialized world-has increased the influence of U.S. programming.

Like the networks, the cable companies find it more profitable to import U.S. progrms than to produce domestic shows. In sddition, cable has made U.S. stations available to many parts to Canada that previously received only one or two Canadian stations.

American influence on Canadion broadcasting has always been a controversial political topic in Canada, although debate has tended to be confined to the country's political, economic and cultural elite.

Largely to protect Canadian broadcasting, the government established the public owned CBC to provide a national network to link Canada's scattered population centers.

Television, therfore, has always been viewed as an instrument of national policy in Canada, although there never have been attempts to influence programming content.

Thus, the commission's report is likely to rekindle a debate within the government about the need for another national inquiry into broadcasting. Two years ago, the government seeiously considered such an inquiry, but dropped the idea when the commision rejected the idea as too time-consuming.