Ministers were "naive" to believe an army of "brilliant people" would spring up to analyse raw spending data for them, a think tank chief says.
The coalition published vast amounts of previously secret data online in the hope that "armchair auditors" would pore over it to discover waste.
But Neil O'Brien, of Policy Exchange, said the new industry never took off as the data was largely "unusable".
The Cabinet Office is attempting to make the data more user-friendly.
Within weeks of coming to power in 2010, the coalition released all items of local authority spending over £500.
Communities Secretary Eric Pickles, speaking at the time, said the move would "unleash an army of armchair auditors and quite rightly make those charged with doling out the pennies stop and think twice about whether they are getting value for money".
The government also published the salaries of thousands of civil servants, naming individuals earning more than £82,900 for the first time, and put online the Combined Online Information System (Coins) database of government spending, which ran to millions of lines of raw data.
But the army of volunteer auditors predicted by Mr Pickles and Cabinet Office Minister Francis Maude - and the boom in "businesses and social entrepreneurs building new applications and services using previously locked-up government data" predicted by the Conservative Party in its 2010 Technology Manifesto - have so far failed to materialise.
Mr O'Brien, whose think tank has been highly influential on Conservative Party policy, said: "I think when they were in opposition the Conservatives were a bit naive about the way they thought they could just stick data out there and brilliant people would come and cut it up and make it very useable.
"That was a bit naive. Things like the Coins database are out there, but in a basically unusable format and if they want that to be a serious driver of transparency they need to enable users to use it in a simpler way."
But, he added, it was a "good thing" to begin government by "forcing" data into the open as it established the principle that it should be publicly available.
Mr O'Brien was speaking at a follow up to the launch of The Big Data Opportunity, a Policy Exchange report claiming the government could save as much as £33bn a year through better data analysis, supported by technology firm EMC.
The report recommends setting up an "advanced analytics team" in the Cabinet Office to identify ways of sharing data across departments, enabling users of public services to save time and money by, for example, accessing data on queue times at airports or doctor's surgeries in real time.
Labour MP Margaret Hodge, chairman of the influential Commons Public Accounts Committee, said "dumping data doesn't help accountability or choice", echoing Mr O'Brien's point that it "didn't lead to a whole band of armchair accountants doing the work for you".
But she said she was in favour of greater transparency - and accused the government of dragging its heels over the promised release of progress reports on major projects, claiming they were worried about revealing problems with the new universal credit system.
The Cabinet Office has been working with data experts at the Open Knowledge Foundation, which recently released an online tool to help journalists and the public search all items of government expenditure over £25,000, to make data more user-friendly and searchable.
Subsequent stages of the project will monitor local councils and other governmental bodies.
It comes as the Cabinet Office released a new strategy for making government websites less confusing and easier for the public to use.