A letter by Albert Einstein in which he refers to God as a creator has sold for £49,000 at auction.

One of the rare examples of an Einstein letter in Italian, to electrical engineer Giovanni Giorgi, it defends his 1915 theory of relativity.

It refers to the criticism of American physicist Dayton Miller, who sought to disprove the theory.

Einstein wrote to Giorgi: "I agree with your opinion on the fact that the movement of an ether with a [mathematical formula] so high is particularly impossible.

"God created the world with more intelligence and elegance."

A spokesman for RR Auction in Massachusetts said the discussion of God as creator was "fascinating".

"Although he did not believe in a personal deity, Einstein was not averse to speaking of God in a scientific context when discussing differing interpretations of quantum physics.

"In 1929, he said that he believed 'in Spinoza's God, who reveals himself in the harmony of all that exists', and in the 1950s he wrote 'If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it.'

"It is this conception of God that appears in the present letter, with the idea of a world designed with 'intelligence and elegance' corresponding with these later notions of structural harmony."

In 2012 Einstein's so-called 'God letter', in which he made clear his disbelief in a biblical God, sold for more than $3 million. Written to the Jewish philosopher Eric Gutkind in 1954 just before Einstein's death, it includes the lines "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. No interpretation, no matter how subtle, can (for me) change this..."