HARRISBURG — Gov. Ed Rendell ended Pennsylvania's distinction of having one of the nation's weakest open-records laws Thursday by signing into law a bill that will open a broader array of government documents to public inspection.

The measure makes sweeping changes to the state's Right-to-Know Law, which was enacted in 1957. It took lawmakers 13 months to agree on a version to send to the governor as they argued over how much information to conceal from average citizens and journalists.

"Is it a perfect bill? No. Is it a good bill? Absolutely. Is it a step on the road to reform? Without a doubt," said Rendell.

The new law, which takes effect in January, will force agencies to disclose all records beyond a list of exceptions, rather than the old law's narrow list of public records available.

Agencies also will be required to justify any decisions to keep records secret. The old law put the legal burden on citizens to prove why a record must be disclosed.

Revising the law became a cornerstone of the Legislature's reform agenda after two dozen lawmakers were voted out in the wake of the 2005 pay raise debacle. The raise, which the General Assembly passed hastily in the middle of one summer night, was later repealed.

Critics of the current law have complained that it saddles citizens with a cumbersome and costly appeal process when their requests are rejected and imposes comparatively weak penalties on officials who violate it.

The new law will establish an office to set policies and deal with disputes. Penalties will be stiffer for agencies that violate the law. And the law requires agencies to respond faster to records requests.