WORCESTER, Mass. (AP) _ A federal bankruptcy court judge ruled Tuesday that the founder of a fundamentalist church must return $6.6 million he duped a chain store heiress into donating through deceit and abuse of his power.

The judge ruled in favor of Elizabeth Dovydenas in her lawsuit against The Bible Speaks church; its founder, Rev. Carl H. Stevens Jr.; and church secretary Kathy Hill for the return of donations made from 1983 to 1986.

''Particularly appalling is (Stevens') insincerity in telling her that her mission from God on earth was to give money to the church, that her money gave her the power to work miracles and that Jonas (her husband) and others were possessed by the devil. He believed none of this,'' Judge James F. Queenan Jr. said in his ruling.

The three-week, non-jury trial that ended April 17 ''revealed an astonishing saga of clerical deceit, avarice and subjugation,'' Queenan said. ''This is a case of undue influence exerted upon a church donor which appears to be unsurpassed in our jurisprudence. The Church cannot, under the cloak of religion, commit wrongs upon the public.''

Mrs. Dovydenas' attorney, Gordon Walker, said his client felt vindicated.

A woman who answered the telephone at the church's Lenox headquarters and refused to give her name referred all calls to attorney Roy Grutman. Grutman's secretary said he was taking a deposition and could not be reached immediately for comment.

Walker said the victory meant churches could no longer claim protection from creditors under the First Amendment, which grants freedom of religious expression.

He said a committee of creditors has submitted a repayment plan, which will be considered at a June 5 hearing.

Mrs. Dovydenas is by far the largest creditor among the group seeking more than $7 million, and the court victory gives her an interest in The Bible Speaks real estate in her Berkshire Hills hometown of Lenox, the attorney said.

The church's isolated headquarters are located on the 69-acre campus of a former school, in one of the weathiest enclaves in the Berkshires. The campus also contains a grammar school and Bible college as well as a 1,300-seat church.

Walker said the repayment plan allows the church at least three years to pay off the claims. Otherwise, he said, church land will be sold.

But Walker said he doubted claims by The Bible Speaks that an adverse court ruling would spell financial disaster for the church, which claims 10,000 followers worldwide.

Mrs. Dovydenas, 34, testified that the 57-year-old pastor and parishioners exploited her unusually susceptible nature by winning her devotion and lying to coax gifts of stock and cash from her.

The church contended she gave willingly and had no second thoughts until her family had her undergo ''deprogramming'' in early 1986.

The judge granted the church temporary protection from creditors, saying in an October decision that Bible was threatened with financial ruin if Mrs. Dovydenas succeeded in her claim.

Mrs. Dovydenas is the daughter of a founder of the Dayton-Hudson Corp., the fifth-largest retail chain in the United States, including such stores as Lechmere. The corporation was valued by Wall Street at $4.4 billion.

She has said the gifts to Bible Speaks amounted to a third of her net worth at the time.

She testified she gave $1 million in early 1985 to stop the migraine headaches of the pastor's fiancee. The heiress said she was duped into thinking the gift worked although the fiancee was hospitalized a short while later.

Mrs. Dovydenas said she gave a $5 million gift later in 1985 when she was told a Bible Speaks pastor was being tortured in Romania for carrying money to an underground church.

She also accused the church of spending at least $350,000 on a Florida condominium outfitted with floor-to-ceiling bedroom mirrors and on lie detector tests and guns for pastors.

The church maintained that most of the gifts went to building a new chapel. The condominium was an investment and the guns and lie detector tests were needed because of threats to pastors' lives, church attorneys said.