Columbia S&L;’s Latest Loss Ups Taxpayers’ Tab : Thrifts: Its third-quarter deficit is $352 million. The hemorrhaging adds up to $1.4 billion during the past five quarters, mainly because of deteriorating junk bonds.

Columbia Savings & Loan, once the nation’s most profitable thrift, on Tuesday posted a $352-million loss in the third quarter as it continued hemorrhaging red ink because of the junk bond market collapse.

The latest results bring Columbia’s losses to a staggering $1.4 billion during the past five quarters. Columbia is insolvent by $710 million and values its junk bond collection, once worth about $4 billion, at just $2.5 billion.

The latest loss will further increase the ultimate costs that taxpayers will bear when Columbia eventually fails and is seized.

Some experts believe that Columbia’s eventual failure will cost taxpayers about $500 million, which would be funds spent to cover deposits up to $100,000 that are insured by the government. But other experts say Columbia will probably cost taxpayers $1 billion or more.

The Beverly Hills-based thrift’s losses have come largely for two reasons: First, companies that issued the risky, high-yield junk bonds have defaulted. In addition, Columbia must lower the value of its portfolio because investors are paying much less for similar issues on the open market.

In the third quarter, the market value of Columbia’s bonds plunged by $226 million, caused in part by increased economic uncertainties in the wake of the Persian Gulf crisis. In a statement, Columbia Chief Executive Edward G. Harshfield described the market drop in August and September as an “unprecedented decline.” He said, however, that Columbia has sufficient cash--it had $1.3 billion in cash and short-term investments on Sept. 30--to meet demands of depositors.

Under normal circumstances, Columbia would have been seized by regulators long ago. But regulators have held off, working with its current management to sell the junk bonds privately so that the government won’t have to inherit them.

The total cost to taxpayers depends on several factors, including how much buyers are willing to pay for its bonds. It also depends on whether Columbia eventually gets a good price for other potentially valuable securities it holds, such as one group issued during the corporate buyout of Safeway Stores by the investment firm Kohlberg Kravis Roberts & Co.

As previously reported, Columbia had earlier agreed to sell its bonds for $3 billion to Gordon America, a Canadian-led partnership, in a deal Columbia would have financed. That deal was scrapped by savings and loan regulators.

Columbia is now negotiating with a group of potential buyers that includes the Wall Street company Goldman, Sachs & Co.; the Lehman Bros. unit of Shearson Lehman Bros. Holdings, and a group led by Salomon Inc. Also included are Gordon America, the investment firm Whitman Hefferman Rhein & Co. and a group led by former Drexel Burnham Lambert executive Leon Black.

Columbia’s latest quarterly losses were offset partly by gains of $50.3 million from the sale of securities, primarily the sale of its investment in the Motel 6 chain.

For the nine months of this year, Columbia lost $781.8 million, compared to $212 million in the first nine months of last year.