The hundreds of thousands of requests that have been received at various levels of government in the last decade have not only been time-consuming for agencies and councils, they have also proved extremely costly.

Such, though, is the side effect of transparency, say the proponents of open government, who also argue that the benefits outweigh the burdens.

“What people often forget is just how much F.O.I. saves money, because it exposes wasteful and extravagant spending,” said Paul Gibbons, a freedom of information campaigner and blogger. “Just one example: a local council in Scotland was spending thousands every year sending a delegation to Japan for a flower festival. Once F.O.I. came into force, they quickly realized they couldn’t justify doing that.”

Before the law, Britain was known for its culture of closed ranks and doctrine of neither confirming nor denying. David Vincent, a professor who teaches social history at the Open University, said the secrecy can be traced to the 1844 postal espionage crisis, when government ministers were accused of opening the letters of Italian exiles. Since then, he said, members of Parliament “had an attitude of essentially, ‘We will only release information if we absolutely have to.’ There was a default policy of nondisclosure.”

Heather Brooke, a British-American journalist who used the government access law in 2009 to obtain details of the expenses of members of Parliament, said she had earlier found a stark difference from the United States. Though information in the United States is frequently held back from reporters by federal, state or local governments, it is often done in defiance of an overall philosophy, if not actual laws, supporting the public’s right to know.