A legislative battle is brewing over proposed changes to the $6 million biotech tax credit law adopted last year.

Legislators next week will consider many changes in the program designed to entice more venture capital firms to take advantage of it.With the funding likely to remain at $6 million this year, some biotech officials are worried that raising the limit on investments from $250,000 to $1 million or more would also limit how many companies benefit.

Venture capitalists want to raise the limit. Bill Snider, managing partner in Broadoak Capital LLC in Bethesda, said he favors increasing the fund to $12 million and making the program permanent, both of which are unlikely this year.

But officials at some companies that benefited last year say leave the law alone.

The law is designed to help small, emerging biotech and biopharma companies get on their feet or stay viable at a time when venture capital for startups is scarce in the state.

David W. Edgerley, secretary of the Department of Business and Economic Development, which manages the fund, said he wants to continue making improvements to the program because it worked so well last year. He said DBED favors maintaining the current limits and that the department fought off a legislative analyst’s recommendation to cut the fund for 2007 to $5 million. He also favors keeping the maximum age for a qualified biotech company at 10 years instead of reducing it to six years, a view shared by the Tech Council of Maryland.

The law allows individuals to invest up to $50,000 in qualified companies. Corporations or venture funds can invest up to $250,000. The value of the state credit is 50 percent of each investment.

Last year, the fund’s entire $6 million was distributed in less than six months. DBED issued 181 credit certificates to investors who in turn invested about $12 million in 20 biotech companies.

The department favors Senate Bill 976, in which any one investor cannot take a credit of more than $900,000, or 15 percent of the total available.

Under House Bill 1007, sponsored by Del. Brian J. Feldman (D-Dist. 15) of Potomac, an investor could take up to $2 million of the fund.

Casey P. Eitner, president and CEO of the research tool company Expression Pathology Inc. in Gaithersburg, said the legislature should leave the program alone.

‘‘Don’t tinker with it,” Eitner said. ‘‘If VCs are lobbying for the amount of $250,000 to go to a $ 1 million, it would only take a couple of them to use up the pool. The important thing is that [tax credits] increase the diversity of the portfolio in bio within the state. The more at-bats you have, the more chance you have to get a hit.”

According to a DBED report, all of the investments that qualified for the credit were made by angel investors, not venture capital funds.

Eitner said the tax credits became available in the middle of his company’s series A round of financing last year.

‘‘We were stalled out because VCs were not that interested in tool companies,” he said. ‘‘Then the tax credit came along and we quickly got $350,000 more to add to a half-million we already raised.”

The tax credit ‘‘helped us tremendously,” helping his company raise $1.5 million, said Marty Zug, vice president of finance at 20-employee Sequella of Rockville, which was founded in 1997 and focuses on tuberculosis prevention and treatment.

The investment made the difference in getting Sequella’s new drug into clinical trials and hiring a new chief medical officer, Zug said.

‘‘Our position is that the bill worked so well last year that there should not be any changes to it,” he said.

Sen. Robert J. Garagiola, (D-Dist. 15) of Germantown, a sponsor of the Senate bill, said, ‘‘Some of the biotech companies in my area would not be able to continue without this program.” He favors increasing the fund to $12 million but will not push the idea because of across-the-board belt-tightening in Annapolis in the face of an expected $1.3 billion budget shortfall.

Linda Powers, managing director of venture firm Toucan Capital Corp. of Bethesda, said startup biotechs in Maryland are caught in ‘‘a perfect storm” of funding challenges.

Investors see a failure of most products to get to the marketplace, highly technical science, a lack of top managers in later clinical-stage development of products and the geography of being in the mid-Atlantic region, she said.

Jonathan Cohen, president and CEO of 20⁄20 GeneSystems Inc. of Rockville, has retained lobbyist David Carroll of Capitol Strategies LLC to help keep the biotech tax credit at least at the same level of success.

‘‘Our position is, ‘Why tinker with it right now?’” Carroll said. Biotechnology ‘‘is not only a major emerging economic driver in Montgomery County, but it is statewide. The sentiment of Jon and a number of companies in the state are to keep the program as is. That points to the success of the program.”

Carroll called Maryland’s program the envy of almost every state. ‘‘It is a true incentivizing program,” he said.