LONDON - Two authors who unsuccessfully sued the publisher of “The Da Vinci Code�? for copyright infringement have been given the go-ahead to challenge their defeat in court.

The Court of Appeal said Wednesday that Judge Timothy Lloyd had granted Michael Baigent and Richard Leigh permission to mount a legal appeal. No date has been set for the hearing, which is expected to begin late this year or early in 2007.

In April, a High Court judge rejected the pair’s claim that Dan Brown’s blockbuster thriller stole central ideas from their 1982 nonfiction book, “The Holy Blood and the Holy Grail.�? Judge Peter Smith said the claim had been based on a “selective number of facts and ideas artificially taken out of (the book) for the purpose of the litigation.�?

Smith ruled that “The Da Vinci Code�? had copied some language from “The Holy Blood and the Holy Grail,�? but said it did not amount to copyright infringement.

Both books explore theories that Jesus married Mary Magdalene, the couple had a child and the bloodline survives.

The media-shy Brown traveled to London to give evidence in the case on behalf of his publisher, Random House, Inc.

In a statement, Random House said it respected Baigent and Leigh’s right to appeal, but regretted “that more time and money is being spent trying to establish a case that was so comprehensively defeated in the High Court.�?

“The Da Vinci Code�? has sold more than 40 million copies — including 12 million hardcovers in the United States — since its release in March 2003. A film version starring Tom Hanks was released in May.

“The Holy Blood and the Holy Grail�? — published by Delacorte Press, a subsidiary of Random House — was a best seller on its release, and climbed sales charts again thanks to publicity surrounding the case.