Officials of Time Inc., continuing corporate efforts to focus on video operations, announced plans today to spin off all forest and paper products subsidiaries into a new, independent firm, a proposal that would cut Time's revenues by a third.

"The reality of our present structure is that between forest products, basically a commodity business, and communications, a consumer services operation, there is no synergy," Time President J. Richard Munro said in remarks before the company's annual shareholders meeting.

Although Munro's announcement represents only the fact that Time's board had authorized management to develop the plan, it was clear from remarks to reporters that the company does not intend to sell the businesses outright.

Time's Forest Products Division operations include Temple-Eastex Inc., a paper and building materials concern, and Inland Container Corp. The division contributed revenue last year of $1.14 billion to Time's total sales of $3.56 billion and has $1.06 billion of the company's $2.89 billion in assets.

Measured by 1982 figures, the divestiture would drop Time from 106th place in the Fortune 500 to 161st place, while the new company would rank 270th.

Under management's tentative plan, shareholders would keep their Time Inc. stock, but would also receive shares in the new forest products company. Time plans to seek Internal Revenue Service approval to retain a 10 percent interest in the new public company. Munro said he hopes the transactions, which have to be approved at a later shareholders meeting, can be completed by the end of the year.