The prosecutor who once led the Democratic fund-raising investigation in Washington said he did not think politics motivated Atty. Gen. Janet Reno to reject his recommendation for an independent counsel. Charles G. LaBella, who lost his assignment after recommending an outside investigation of President Clinton and other top White House figures, also said such an inquiry might well have failed to produce criminal charges. "The standard was information, sufficient information from credible sources. . . . I believe we had substantial information from credible sources to warrant a full-scale investigation of many of these allegations," LaBella said on NBC-TV's "Meet the Press."