Public bodies have been criticised for failing to respond to requests under the Freedom of Information Act.
Kevin Dunion is calling on public bodies for radical improvements
Scottish Information Commissioner Kevin Dunion said authorities often only released information months late after appeals to his office.
The first Information Commissioner annual report since the law came into force showed his office received nearly 600 appeals and almost 2,500 inquiries.
Mr Dunion said public bodies needed to make radical improvements.
Nearly one in five appeals involved authorities which had failed to respond to requests for information.
Kevin Dunion emphasised that more than half the appeals came from ordinary members of the public.
Solicitors and journalists accounted for more than a quarter of appeals.
The Scottish Executive is carrying out a public consultation on how the Freedom of Information Act is working.
Mr Dunion described the act's first year as a "great success".
Speaking to BBC Radio's Good Morning Scotland programme, he said: "We didn't know a year ago how many people would ask for information, how authorities would respond, would know how to appeal to my office and we've had answers to all of those questions.
"Tens of thousands of people have made requests, authorities by and large have responded extremely well and I've received over 570 appeals to my office - far more than I had anticipated but it reflects how the act has been enthusiastically used by the Scottish public."
But he added: "A third of all appeals to my office are upheld entirely so it is quite clear that there are instances where Scottish public authorities should be releasing information and are not."
Mr Dunion also warned against any changes to the act which would detract from the right to information and more transparency and accountability.
He said: "I appreciate that Scottish public authorities had only a short period in which to prepare their organisations for the act coming into force, but the duty to respond within 20 working days is not particularly onerous in most cases.
"I hope to see a radical improvement in this area in 2006."