Thousands of public bodies are ill-prepared for the Freedom of Information Act, due to come into force next month, says an influential group of MPs.
High staff turnover at the DCA means few are ready, say MPs
From next month anyone will have the power to demand information from a range of public bodies - from Whitehall departments to doctors' surgeries.
But an all-party committee said it was "not confident" many would be ready.
It blamed a "lack of consistent leadership" from the government. But ministers say they have given help.
The act comes into effect in England, Wales and Northern Ireland, on 1 January while similar measures are being brought in at the same time in Scotland.
It provides the public with a right of access to information held by about 100,000 public bodies, subject to various exemptions.
Doctor's surgeries are among those targeted by new legislation
The government department responsible for implementing the change suffered from an "unusually high turnover" of staff within the department, which had "seriously interfered" with its work, said the Constitutional Affairs Select Committee.
It said, despite four years of preparations, some local authorities and parts of the health sector were still not ready.
The Department of Constitutional Affairs had "failed" to provide early guidance on technical matters and shown a "lack of consistent leadership", the MPs found.
Committee chairman Alan Beith said: "The DCA has had four years to prepare for freedom of information, but with less than a month to go it appears that some bodies may not be well enough prepared.
"Our report shows that in the past support and guidance from the DCA, which has overall responsibility for guiding the public sector through the process of implementation for the freedom of information regime, has been lacking."
Mr Beith later told BBC News he hoped the committee would be proved wrong.
"The situation we have from 1 January is that the burden of proof is on government to show you should not have information rather than on you to prove to government you are entitled to it," he said.
"That is such a cultural change that we would like to have seen it well under way sooner."
But Constitutional Affairs Secretary Lord Falconer said a huge amount of work had been done.
He said: "Our focus has been on making sure that central government is prepared for a change but we have also provided guidance and help and support for the hundred thousand other public authorities."
Each body had to develop its own arrangements, he argued.
"Local authorities are already under obligation to provide various sorts of information and would, I would have thought, in many cases be very well prepared," Lord Falconer continued.
"But inevitably in a move of this importance, which I very much hope will make a cultural change, some people will be better prepared than others."
A spokesman for the DCA added: "The department has delivered a simple, liberal fees regime, guidance on the Act which has been widely praised, and expert networks of staff working on freedom of information implementation."