Independent counsel Whitney North Seymour Jr. accused the Canadian government and the Justice and State departments yesterday of creating a sensationalized and unfounded "cause celebre" out of his request for a diplomat's testimony.

Seymour, who is prosecuting former White House deputy chief of staff Michael K. Deaver on perjury charges, was responding to a Justice Department complaint about his conduct filed with the U.S. District judge in the Deaver case. In a 10-page response, he called it "a partisan document . . . wholly without merit and . . . an inexcusable attempt to embroil the court in a political controversy."

The Justice Department had attacked him earlier and Canada, he suggested, wanted "to divert attention from the unpleasant truth."

Canada was one of Deaver's major lobbying clients after he left the White House. Seymour has accused Deaver of lying about his contacts with top Reagan administration officials, contacts he allegedly made on behalf of Canada and others.

Seymour called charges that he breached an agreement with Justice Department officials by seeking the testimony of Canadian Ambassador Allan Gotlieb a second time "a complete fabrication." He insisted all his contacts with Canada's government were proper.

"It is true that I owe him {Seymour} an apology," Justice spokesman Patrick S. Korten said last night. "It is incorrect to say that there was an agreement" binding Seymour to make all his Canadian contacts through diplomatic channels.

But Korten said Seymour's effort to subpoena the ambassador still "has created serious difficulties for us with one of our closest allies."