LONDON - Some of Britain's gold reserves suffered surface cracks when they were cast 50 years ago in New York, but the purity of the Bank of England's bullion was not affected, the central bank said on Sunday.

The BoE was moved to issue a statement clarifying the purity of its gold after the Times newspaper on Saturday ran a report saying some of the gold might have a purity of just 91 per cent.

The Times' report followed the BoE responding to a Freedom of Information request by the trade journal Metal Bulletin.

Britain has 320 metric tons in gold reserves worth around 4 billion pounds ($8.12 billion).

"All gold held by the Bank is between 99.5 and 99.9 per cent pure, the standard set by the London Bullion Market Association (LBMA), and has been assayed and stamped as such," said the BoE is its statement.

"The purity of the gold held by the Bank has not been questioned by the LBMA."

"Some gold cast into bars in New York about half a century or more ago developed surface cracks at that time, while the metal was cooling immediately after casting. This minor issue appears to be behind the inaccurate report."

The BoE is now in talks with the LBMA to decide whether the bars with the surface cracks do meet recently revised standards for gold traded in the market -- known as London good delivery bars.

If these bars do not meet this new standard then the BoE will have to re-melt them.

"The cost of re-melting the bars would be an insignificant proportion of their value and the bars concerned represent a small proportion of the gold held by the Bank," the BoE statement added, without specifying how many bars were affected.

"The issue of lower casting standards at one gold refinery many decades ago is not confined to gold stored at the Bank of England."