The Federal Trade Commission is raising the ante in its antitrust confrontation with Google with the commission staff preparing a recommendation that the government sue the search giant.

The government’s escalating pursuit of Google is the most far-reaching antitrust investigation of a corporation since the landmark federal case against Microsoft in the late 1990s. The agency’s central focus is whether Google manipulates search results to favor its own products, and makes it harder for competitors and their products to appear prominently on a results page.

The staff recommendation is in a detailed draft memo of more than 100 pages that is being shared with the five F.T.C. commissioners, said two people briefed on the inquiry.

The memo is still being edited and changes could be made, but these are mostly fine-tuning and will not alter the broad conclusions reached after an inquiry that began more than a year ago, said these people, who spoke on the condition that they not be identified.