The 30-year-rule will be reduced to 20, the prime minister says
Public bodies should automatically release all information that does not need to stay secret, the information commissioner is expected to argue.
Richard Thomas, who is stepping down, will say all but the "crown jewels" should be released without waiting for Freedom of Information (FOI) requests.
He will add that the MPs' expenses row was a "coming of age" for openness.
His speech comes a day after proposals to keep cabinet papers exempt from FOI laws for 20 years were announced.
According to an advance text released by his office, Mr Thomas will say the public now expects to be treated as "grown ups".
He will say the leak of MPs' details to the Daily Telegraph, following a court ruling that they must be disclosed, "cemented FoI's reputation as a success story".
Mr Thomas, who is due to stand down before the end of June 2009, will call for a state of affairs where "openness is the norm" within the public sector.
"Public authorities must earn the trust and confidence of the public," he will add.
"They should identify their crown jewels - the information that really cannot be made public - and ensure that other official information is routinely disclosed without waiting for requests."
His intervention comes a day after Prime Minister Gordon Brown unveiled proposals to reduce the "30-year-rule" on the publication of government papers and extend FOI to cover private firms doing work for the public sector.
BBC News' Freedom of Information expert Martin Rosenbaum said the new proposals announced by Mr Brown in the Commons meant cabinet papers, including those for cabinet sub-committees, would be exempt from FOI for 20 years.
The Information Tribunal - which rules on appeals against Freedom of Information requests - ordered ministers in January to release minutes of cabinet meetings which discussed the 2003 Iraq invasion arguing it was in the public interest.
But the government vetoed the request under Section 53 of the FOI Act, arguing it could do "serious damage" to cabinet government which outweighed the public interest needs.
'Public interest' test
The decision to release details of Cabinet discussions currently rests on a "public interest" test.
Mr Brown has said he wants to extend the scope of the Freedom of Information Act as part of wide-ranging constitutional reforms.
He also wants to cut the limit on publishing official papers - but give more protection to sensitive material.
Such material would also include papers relating to the Royal Family as well as discussions between senior ministers.
Maurice Frankel, director of the Campaign for Freedom of Information, said requests for cabinet papers from five or 10 years previously should be considered on their merits.
"To exclude the whole class of cabinet papers from the act is an unnecessary, retrograde step, which will protect much material that does not need to be confidential and allow the top of level of government to operate in absolute secrecy," he added.
In a statement, the Ministry of Justice said a recent review into releasing government papers had recommended "enhanced protection" for some papers be looked at.
The MoJ said it had since looked at "important safeguards in the current FOI Act".