A senior Quebec separatist leader has decided to quit Premier Rene Levesque's Cabinet in the first major split within the ruling Parti Quebecois.

Robert Burns, 42, minister of state for parliamentary reform, was quoted as saying that he was resigning because hecause he believe that Levesque would lose both the planned referendum on Quebec sovereighty and the next provincial election. "I donht want to be there when it happens," Burns said.

Burns was the key separatist spokesman in the Quebec National Assembly before the Parti Quebecois swept in to power in 1976. It is known that he and Levesque did not get along well, and that the premier reputedly feels threatened by Burns' popularity.

Levesque confirmed last night that Burns was leaving for "health reasons."

Asked to comment on his referendum to take the French-speaking province out of the Canadian federation while remaining linked in a economic association, Levesque said that "if it were held today, it's true, we would lose it." He added, however, that after next Tuesday's federal elec-of the future [and] I am sure we will win the referendum."

Burns, who frequently criticized Levesque's pragmatic approach, told reporters that the Parti Quebecois would get around 32 percent of the votes in the referendum.

The Levesque-Burns rift appears to reflect policy disagreements in the Parti Quebecois following a severe setback it suffered in two recent by-elections.

The defeats, which were by massive margins, appear to have slowed the momentum of the separatist forces who, until this month, were steadily gaining strength according to the polls.

Although a socialist-minded economist, Burns has been conservative on a number of issues. He let it beknown that he was increasingly isolated and surrounded by what he termed too many "power-hungry egomaniacs."

There appears to be a considerable disaffection with Levesquehs policies. In a recent newspaper article, Robert Barberis, one of the party's most active members, criticized Levesque for having turned the organization into a tool of his policies.

There has been considerable opposition to Levesque's attempt to back a small Social Credit group in the current federal elections as a way of defeating Prime Minister Pierre Trudeau's Liberals in Quebec.

More strident separatists feel that such pragmatic moves represent a backtracking on social reforms and independence.