People have the right to access information held by 100,000 public bodies now the Freedom of Information Act has come into force.
Government departments say they are following rules on public records
From the start of the New Year, police forces, hospitals, schools, local councils and the government are obliged to reply to requests for information.
The act was passed by parliament four years ago but has only just become law.
Government officials have denied claims by the Tories that systematic shredding of documents was taking place in the build-up to the act's implementation.
Secretary of State for Constitutional Affairs Lord Falconer said he believed the Act would have a major impact on the way government is conducted and defended the shredding of documents.
He told BBC Radio 4's Today programme: "Good document management requires that after a period of time you get rid of it.
'Right to know'
"It is very unfair to characterise it as being an attempt to thwart the Act - it is trying to get documents in order."
Britain's information commissioner Richard Thomas has also said there is "no hard evidence" that files are being wrongly destroyed to prevent disclosure.
From Saturday, people will be able to access information on how decisions are made and how public money is spent.
Anyone, of any nationality, and living anywhere in the world, will be able to make a written request for information, and expect a response within 20 working days. For the majority, there will be no charge.
Lord Falconer added: "The need to know culture has been replaced by a statutory right to know. Previously invisible information will become visible.
"I am convinced that the laws which take effect today will make government more open, and the balances we have built into the system will ensure that effectiveness is not compromised.
"Good government is open government, and good government is effective government.
"Our long-term goal is strengthen the link between the state and the citizen."
Despite the effort to make the workings of public bodies more transparent, requests can be rejected on cost or public interest grounds.