For the third time in four years, Congress is debating a bill designed to give small companies greater access to venture capital.

The bill would create a federally-chartered, private Corporation for Small Business Investment (COSBI) and thus privatize the 30-year-old Small Business Investment Company Program administered with taxpayer-guaranteed loans by the U.S. Small Business Administration (SBA).SBA licenses and supervises privately-organized and owned small business investment companies (SBICs), which extend long-term and equity capital financing to small firms. SBICs must first raise at least $1 million of their own monies and, after being licensed by SBA, can get up to three SBA-guaranteed debenture dollars for every dollar of private capital.

There currently are 445 SBICs in the country. Of those, 128 are directed toward minorities. In the last fiscal year, the SBICs extended about $550 million worth of loans and equity capital to small companies.

The House Small Business Committee has approved the COSBI legislation, and the Senate Small Business Committee is expected to approve its own version. But a major difference in the bills has developed, with the Senate measure giving SBA broad regulatory powers over COSBI.

Rep. John LaFalce, D-N.Y., chairman of the House Small Business Committee, says creation of COSBI would give SBICs a more reliable source of funding and make more capital venture funds available, much like the Federal National Mortgage Association (Fannie Mae) has broadened financing for the housing industry.

The COSBI bill is supported by the U.S. Chamber of Commerce and the National Association of Small Business Investment Companies. Support also has been expressed by the Democratic National Committee's Small Business Council and the Republican National Committee's Small Business Advisory Council.

But the Reagan administration, which is generally against creating any new government-sponsored enterprise, opposes COSBI. Budget cost is one reason. SBA Administrator James Abdnor, a Reagan appointee, told the House committee that transferring the SBIC program to COSBI would involve the transfer of more than $1 billion in taxpayer funds without any regulation. The Treasury Department contends that the government would be providing COSBI with up to $1.8 billion, either directly or indirectly.

The House bill addresses some of the administration's concerns, including giving Treasury the right to disapprove the issuance of COSBI obligations if they would impair the private corporation's financial safety. The House committee also dropped a provision exempting COSBI from state and local taxes.

The COSBI legislation would create a private corporation with a 15-member board. Present and new SBICs wishing to affiliate with COSBI would have to buy corporation stock in an amount equal to one percent of their private capital and SBA-guaranteed debentures. SBICs choosing not to link up with COSBI would go out of existence within two years of paying back their government-backed debentures.

COSBI would buy the outstanding $720 million portfolio of SBIC debentures guaranteed by SBA, and the government would be responsible for paying off all COSBI member defaults. Securities issued by COSBI to private investors would not be guaranteed by the government, but the Treasury could buy up to $500 million in COSBI securities if the corporation ran into money problems.

Like SBA's other financial assistance programs, the SBIC program has had its successes and failures. SBA-backed SBICs have helped finance such glamor companies as Wang Laboratories, Apple Computer and Federal Express and innumerable other small and successful companies which might otherwise have had great trouble getting capital from traditional lenders.

But the program has been peppered with failures, too, and they have cost the taxpayers millions of dollars since 1958, when the program got started on orders from Congress. SBICs in past years have financed such questionable enterprises as a rock concert promoter, a string of X-rated movie houses and a group of Turkish baths. And a minority SBIC in California once helped finance "disadvantaged" doctors and dentists, some of whom already earned up to $500,000 a year.