The Canadian government has taken the offensive in its campaign against independence for Quebec with charges that the Canadian Broadcasting Corp., the stateowned television and radio system, is riddled with separatist sympathizers.

Prime Minister Pierre Elliot Trudeau and several of his senior Cabinet ministers say Quebec nationalists have quietly taken over Radio Canada, the French-language service of CBC, and are systematically distorting news and public affairs programs to favor the separatist government of Quebec Premier Rene Levesque.

The allegations have caused a political uprear here because Trudeau and his ministers have so far failed to produce hard evidence to back up the charges.

CBC President A.W. Johnson threatened today to quit if the government interfores in the network's programs and said he was surprised and dismayed by the intensity of the ruling Liberal Party's attacks.

The Quebec government has in fact been softpedaling the separatist issue. Levesque's separatist Parti Quebecois defeated the provincial Liberal government in November. But Levesque is playing down his party's commitment to make Quebec an independent republic.

Levesque never mentioned the words separatism or independence in a rambling inaugural speech last week at the opening of the Quebec legislature, known as the National Assembly.

He did say that his government would introduce a bill within several months to hold a provincial referendum on separatism. That vote, to be conducted some time before Levesque's five-year mandate runs out, is considered to be the crucial test of whether the 7 million predominantly French speaking Quebec residents desire independence.

Trudeau and his ministers began their attack on Radio Canada shortly after the November election and last week Trudeau asked the Canadian Radio-Television and Telecommunications Commission, the federal communications agency, to conduct an inquiry by July 1.

CBC operates national television and radio networks in both English and French, the two official languages of Canada. Most of the French programs are broadcast within Quebec, although there are French CBC stations across the country. The agency will receive $467 million in federal government subsidies this year and is required by law to promote and protect the national unity.

Trudeau and other Liberal leaders say they have received thousands of complaints from Quebecois about Radio Canada's pro-separatist bias.

Urban Affairs Minister Andre Ouellet claims to have a list of separatist supporters on the CBC payroll, but he has not produced it.

Trudeau says he is convinced that "the overwhelming majority" of French-language CBC employees are separatists.

"I would not put a militant atheist at the head of religious programs," he said. "When you have 10 militant atheists at the head of 10 religious programs you begin to wonder if the system isn't a little bit biased."

Trudeau said an inquiry was needed "before it's too late, before they've converted everyone to atheism."

Opposition parties in Parliament say the whole thing is a Liberal witchhunt to divert public attention from more serious problems of high unemployment and inflation. There has also been in outery in the press, with charges that the inquiry and the attacks on CBC are a threat to freedom of speech. Two unions representing about 7,000 CBC employees have also denounced the government's tactics.

Trudeau said his mail reflected "an agonized cry" among Quebec residents about CBC bias but Harry Boyle, head of the regulatory agency conducing the inquiry, said Trudeau's office gave him only one letter complaining of such activities.

Boyle's agency has received only five letters about Trudeau's demand for an inquiry, three supporting the idea and two rejecting it. Boyle said yesterday he had still received no hard evidence to back up the liberal charges.

Boyle has asked all members of Parliament to come forward with any specific charges before mid-April so that the inquiry may be completed.