Saad Eddin Ibrahim, who has been living outside of Egypt for a year, was convicted in absentia after writing several opinion columns in mostly U.S. newspapers that criticized Mubarak and called for the Bush administration to cut aid to Egypt.
In his ruling, Judge Hisham Bashir said Ibrahim made false claims and tarnished Egypt's image through his writings in the "foreign press."
Bashir did not specify a particular newspaper. In an August 2007 column in the
The allegations against Ibrahim were first made by a former and current ruling party leaders who filed lawsuits against him. Egyptian law allows private citizens to file lawsuits against individuals for allegations that damage society, and the lawsuits can carry criminal convictions.
Ibrahim's lawyer, Shady Talaat, described the court ruling as flawed and vowed to appeal it.
"How come a court gives individuals the right to sue each other in cases related to national security and interests? Issues like these should be handled by intelligence, state security and other institutions," Talaat told The Associated Press.
The case against 69-year-old Ibrahim is among a series of lawsuits filed by members and loyalists of Egypt's ruling party against government critics, aiming at intimidating opposition. Earlier this year, the editor of an independent Egyptian newspaper was sentenced to six months in prison for reporting on Mubarak's alleged health problems.
One of Egypt's best known democracy advocates, Ibrahim was among the first to publicly criticize the grooming of Mubarak's son, Gamal, to succeed him and was charged with tarnishing Egypt's reputation in 2000. He spent years in jail until a three-year odyssey of trials and appeals ultimately resulted in his acquittal.
Ibrahim has also advocated cutting Egypt's $1.3 billion in U.S. military aid to pressure for democratic reforms.
Egypt-U.S. relations were strained after Congress passed a bill late last year that called for withholding $100 million of Egypt's total $2 billion in aid until the country took steps to improve human rights and stop arm smuggling into the Gaza Strip.
Egypt had denounced the aid withholding as unacceptable interference in internal affairs. Ibrahim had believed Egypt held him responsible for the legislation because it was proposed only days after the democracy advocate spoke with President Bush at a summit of dissidents from around the world.
However, in March, Secretary of State Condoleezza Rice said she waived legislation in a nod to one of Washington's top Mideast allies.
Talaat said he did not know where Ibrahim was currently living. The scholar has been traveling between the United States, Qatar and Spain since June 2007 and has repeatedly expressed fear of arrest if he returned to Egypt.
If Ibrahim returns to Egypt, he would be eligible to remain free on bail while a court decides his appeal, but he is likely to remain out of the country until a final court ruling, Talaat said.