A letter being auctioned in London tomorrow adds more fuel to the long-simmering debate about the Nobel Prize-winning physicist's religious views. In the note, written the year before his death, he dismissed the idea of God as the product of human weakness and the Bible as "pretty childish."

The letter, handwritten in German, is being sold by Bloomsbury Auctions and is expected to fetch $12,000 to $16,000.

Einstein, who helped unravel the mysteries of the universe with his theory of relativity, expressed complex and arguably contradictory views on faith, perceiving a universe suffused with spirituality while rejecting organized religion.

The letter up for sale, written to the philosopher Eric Gutkind in January 1954, suggests his views on religion did not mellow with age.

In it, he said: "The word God is for me nothing more than the expression and product of human weaknesses, the Bible a collection of honorable but still primitive legends which are nevertheless pretty childish."

"For me," he said, "the Jewish religion like all other religions is an incarnation of the most childish superstitions."

Addressing the idea that the Jews were God's chosen people, he wrote: "As far as my experience goes, they are also no better than other human groups, although they are protected from the worst cancers by a lack of power. Otherwise I cannot see anything 'chosen' about them."

Bloomsbury spokesman Richard Caton said the auction house was "100 percent certain" of the letter's authenticity. It is being offered at auction for the first time, by a private vendor.

John Brooke, emeritus professor of science and religion at Oxford University, said the letter lent weight to the notion that "Einstein was not a conventional theist" - although he was not an atheist, either.

"Like many great scientists of the past, he is rather quirky about religion, and not always consistent from one period to another," Brooke said.

In later life, he expressed a sense of wonder at the universe and its mysteries - what he called a "cosmic religious feeling" - and famously said: "Science without religion is lame, religion without science is blind."

But he also said: "I do not believe in the God of theology who rewards good and punishes evil. My God created laws that take care of that. His universe is not ruled by wishful thinking, but by immutable laws."