A federal Ethics Advisory Board informally agreed yesterday that the government should end a five-year ban on federally funded test-tube baby projects.

The agreement was reached near the end of nearly two days of hard debate at the Department of Health, Education and Welfare. Board members said they expect to vote officially next month that creating human embryos in the laboratory is ethical if the sim is to implant or to learn to implant them in mothers.

The board must act to gain knowledge and set rules, said Dr. Mitchell Spellman of Harvard University. Otherwise, he warned, the technique will be spread by profit-seeking but ill-informed doctors, and "there could be another catastrophe like thalidomide."

The federally set ban has officially affected only HEW-funded research. But the moratorium's spirit -- and agonizing ethical questions over starting, and sometimes ending, life in a laboratory vessel -- have choked off all such efforts since 1974.

A majority of the 13-member board, it become clear, also is ready to recommend that the government may fund some such efforts. It should do so, members said, only where the knowledge gained would help assure that any resulting children will be normal.

On the board meting's first day, the Rev. Richard McCormick of Georgetown University, a prominent Catholic moral scholar, argued against any studies in which a sperm and female egg cell might be joined just for study, without placing the consequent living, growing cell mass into the woman who provided the egg.

Yesterday he agreed that some research is needed in which scientists merely examine the cell mass and subject it to chromosome analysis to learn whether the method might produce some defective children.

The scholar-priest conceded that such research, though it ends with the embryo being sacrificed. is "a necessary evil" if thousands of infertile women are to be offered this way of bearing their own child safely.

He said he also is ready to agree that the government should fund some research, though he has raised objections to federal financing in the past. He said he still thinks the government should not fund actual medical services to create test-tube pregnancies.

The 11 men and two women on the board -- named by HEW Secretary Joseph A. Califano Jr. -- agreed that they were facing what one called "a terrible dilemma."

On the one hand, they said, there is still great uncertainty that the method will produce normal babies. Since last July a British team has achieved two live births, but two other babies died in pregnancy, one with a chromosome abnormality.

On the other hand, said board members, clinics in serval parts of the United States and Europe are getting ready to provide such services whether governments approve them or not.

"It is clear that the world is about to embark on a procedure for which there are no rules," said James Gaither, San Francisco attorney and board chairman.

"I don't think anyone on the board says the department [of HEW] should fund such research. But I believe most of us are ready to say that we see no ethical objections."

The recommendation the board is expected to approve would allow implantation of a laboratory-born embryo into a mother only among married couples who themselves contribute the sperm and egg. Any embryo for study alone would have to come from donors who have been fully informed of the study's aim and given consent.

No embryo could be sustained in the laboratory beyond 14 days -- about the date at which it would be placed into a mother if a pregancy were intended.