A five-member team appointed by Congress to investigate the killing has said there is no evidence of a conspiracy. But it slammed the US Government for decades of secrecy over the assassination.

'Needless and wasteful'

The team's 208-page report called on the government to change the "current practice of excessive classification of historical documents".

It said making such material public was essential to maintaining freedom.

It added: "The review board's experience leaves little doubt that the federal government needlessly and wastefully classified and then withheld from public access countless important records that did not require such treatment."

Such secrecy, "led the American public to believe that the government had something to hide", it added

No answer to the big question

The board - a federal judge, three historians and one archivist - examined millions of old and new documents and interviewed people, some for the first time.

But it did not address the question of who killed Kennedy.

Investigations into the assassination of Kennedy 35 years ago in Dallas, Texas, have caused much controversy and sparked a number of conspiracy theories.

The board examined new information about events in Dallas, the alleged assassin Lee Harvey Oswald, the presidential autopsy, photographs and reactions of government agencies to the assassination

But despite its access to millions of records the board did not have in its mandate the authority to re-open the investigation.

James Lesar, director of an independent US organisation researching the assassination, said questions remained unanswered.

"We still have an unsolved assassination of a president of the United States that is not being investigated," he said.