A lobbying group founded by Ralph Nader charged this week that Sen. Jake Garn, R-Utah, "is a major stumbling block" in a Senate-House conference on legislation to deal with billions of dollars in losses suffered by federally insured savings and loan institutions.

The conference, called to work out differences between House and Senate versions of the bill, is deadlocked. Senior members of both the House and Senate banking committees, including Garn, were meeting Tuesday to try to set up a framework for an agreement before Congress recesses Aug. 4.Garn called the Nader accusations "reckless" and said "they do not accurately reflect my positions."

Nader and Garn have had numerous bitter confrontations dating to a hearing in 1977 at which Nader invoked the memory of Garn's first wife, who died in an auto accident, to push seat-belt legislation.

Banking committee staffers have estimated that S&L losses are costing the nation $20 million a day.

The group, known as Public Citizen, said Garn, the ranking Republican on the Senate committee, "opposes every measure that would protect consumers or save taxpayers money."

Sherry Ettleson, an attorney for Congress Watch, another Nader-founded group, said Garn is attempting to impose "the most costly alternative (and) will put a major portion of that cost on the backs of the average American."

Ettleson said Congress Watch opposes Garn's support for M. Danny Wall, a former Salt Lake housing director, as head of the new Office of Savings Associations. She said Wall, who was appointed to head the Federal Home Loan Bank Board in 1987 after the S&L crisis erupted "led the savings industry down the road to ruin."

Garn retorted that Wall went to the FHLBB only after the crisis was known and after Garn had sponsored and won Senate approval of a bill to rescue the S&L industry at an estimated cost of $15 billion. That bill died in the House when Speaker Jim Wright, D-Texas, refused to bring it to the floor in the waning days of the 1986 session.

Nader, Garn said "is in total disregard of the facts."

The Nader group said Garn would allow S&L's to continue to invest in junk bonds. Garn said he favored cutting such bond investments from a limit of 11 percent to 6 percent. He denied that he wanted to allow the new S&L watchdog agency to operate "behind closed doors," as the group claimed.