Roger Smethurst, Head of Knowledge and Information Management at the Cabinet Office, responding to a Freedom of Information request, said that the findings of the market research in January on "attitudes in Scotland towards Scottish independence" would remain secret under section 35(1a) of the Freedom of Information Act, which exempts disclosure of information if it relates to the formation of UK Government policy.
He admitted there was a general public interest in the disclosure of information to encourage public understanding of the issues involved in formulating government policy and a specific public interest in promoting wider understanding of the issues raised by the independence referendum.
But Mr Smethurst said these had to be balanced against the public interest in ensuring Coalition Ministers and officials could continue to formulate and develop policy on this subject; market research, he insisted, was an "essential tool" in that.
It was crucial, he said, that Ministers and their advisers could "freely and without inhibition" use this research to explore all aspects of the issues raised by the referendum.
"It is essential this research remains confidential so that ministers and their advisers can carry out this role effectively and debate such matters with candour," explained Mr Smethurst, adding: "Taking into account all the circumstances of this case, I have concluded the balance of the public interest favours withholding the information."
A Scottish Government source responded by saying: "David Cameron's Government have spent almost £50,000 of taxpayers' cash on opinion polling about independence, which they are determined to keep secret, even under Freedom of Information laws. That is totally unacceptable and totally unsustainable.
"No matter how uncomfortable the results may be for Westminster and the No campaign, they must publish the findings," he added.