Opponents of the new test-tube baby clinic in Norfolk lost their bid today for a Virginia law banning genetic engineering and other forms of experimentation on unborn human organisms.

Del. Lawrence D. Pratt (R-Fairfax), sponsor of the proposed ban, said he realized that his bill was headed for certain defeat but urged the House Health, Welfare and Institutions Committee to study it for next year's General Assembly session. The committee rejected his plea.

Pratt, who has questioned the state Department of Health's approval of the clinic last month, said his bill would not prevent the clinic from operating so long as doctors refrained from artificially fertilizing more than one egg at a time from each female patient.

But clinic officials argued that approval of the bill would be a first step toward halting important genetic research into inheritable diseases such as diabetes and an impediment to medical research in general.

"Would we stop our attempts to eradicate smallpox, polio and even cancer from the face of the earth because we are 'interfering' with natural processes?" asked Mason Andrews, founder of the clinic. "I think not."

The clinic's procedure calls for removing an egg from an ovary of a woman unable to conceive a child by other means, fertilizing it with sperm from her husband, then transplanting the fertilized egg into her womb.

Pratt and clinic opponents fear that test-tube baby researchers may be tempted to fertilize several eggs from each woman, then lay aside the extra embroyos for experimentation. Pratt said his bill would ban those kind of "abuses in the laboratory."

Andrews and other supporters have insisted the clinic would follow strict federal ethical guidelines and would only fertilize one egg per woman at a time using only sperm from the woman's husband. They have argued that the clinic -- the nation's first using so-called in vitro fertilization -- is a potential blessing for couples who cannot conceive children by other means.

In another action, the House of Delegates today gave preliminary approval by a 47-to-45 vote to a bill that would grant a credit to low-income and elderly families forced to pay the state sales tax on food.

The bill is a compromise measure reluctantly agreed to by lawmakers who favored total repeal of the food tax after they realized they lacked the votes to get the repeal through the House Finance Committee.

"People have been telling us for years and years and years that we ought to get rid of the sales tax on food," said the bill's chief sponsor, Del. Warren G. Stambaugh (D-Arlington). "This is as close as we're going to get to give some real tax relief . . . to people who need it."

Del. George W. Jones (R-Chesterfield) denounced the bill as a "welfare bill, pure and simple" that would only help those on welfare programs and not the middle class. "I think we are really trying to fool the people of Virginia."

Jones' motion to refer the bill to the Appropriations Committee, where it would likely have been killed, lost 54 to 35. The House then narrowly voted preliminary approval for the bill. The measure comes up for a final vote tomorrow, and if approved, must then pass the Senate.