Health, Education and Welfare Secretary Joseph A. Califano Jr. said yesterday he has asked for FBI assistance in his department's investigations into Medicare and Medicaid fraud.

"I've talked with Attorney General (Griffin B.) Bell in the last few days and we're going to put FBI agents full blast into the Medicare and Medicaid frand investigations until we can get out Office of Investigations in NEW up to full speed," Califano said on the interview program "Meet the Press" (NBC, WRC).

Califano said HEW has combined the Medicare and Medicaid investigations "in order to give us a better opportunity to root out fraud."

"I've also strongly and personally gone to Capitol Hill to support H.R. 3 (legislation) to make it a felony to steal people's money" through welfare fraud, he said.

The HEW Secretary made the statements in denying had sought to impede a department investigation into alleged fraud involving a San Jose, Calif., firm that uses Medicare and Medicaid money to provide health care to the poor and the aged.

Califano and his choice for HEW under secretary, Hale Champion, were accused by John J. Walsh, former chief investigator for HEW, of attempting to block the investigation.

Walsh made the allegations Thursday in a sworn affidavit filed with the Senate Finance Committee. He said he had quit his job after being told by Califano that his investigations had to be cleared by HEW's general counsel.

"I did not in any way hinder or impede out fraud investigation - and nor did Mr. Champion - in California or elsewhere," Califano said yesterday. "Everything that I've done in this area has been designed to make those investigations go faster and better."

On another matter, Califano said he is studying whether the law under which the Food and Drug Administration wants to ban saccharin should be changed.

The 1958 measure sponsored by Rep. James J. Delaney (D-N.Y.), requires the FDA to ban any food additive known to cause cancer in animals or humans.

The FDA, acting on the basis of Canadian tests that showed saccharin-caused tumors in some rats, on March 9 announced its intention to ban saccharin, but said any such action would not take effect until July at the earliest.

Califano said HEW will soon recommend to Congress what to do about the so-called Delaney amendment. But he said the recommendation probably will not come during this week's hearings on the matter before the House Commerce Subcommittee on Health and the Environment.

Rep. Paul G. Rogers (D-Fla.), subcommittee chairman, was quoted yesterday by the Associated Press as saying that it may be necessary to liberalize the amendment.

"It is completely inflexible; it allows for setting no tolerance level," Rogers was quoted as saying. AP also said Rogers was not convinced that the Canadian test proved the carcinogenicity of saccharin.

Califano said he is staying out of the saccharin dispute, because, as a private attorney, he once represented the Coca-Cola Co., which uses the additive in its diet drinks.

Califano said his decision is based "more on a matter of appearance" of possible conflict of interest than an actual conflict.