PN leader Adrian Delia laid a wreath at the makeshift memorial to Daphne Caruana Galizia in Valletta on Tuesday to mark one year since her murder.
The Nationalist Party said that a year since the assassination, the people were still awaiting justice.
The party has joined calls for a public inquiry.
"This murder has seriously threatened freedom of expression, the protection of journalists and the rule of law. Justice must not only be done, but be seen to be done," the PN said.
READ: Anyone responsible for the murder will be found, government vows
Dr Delia was accompanied by PN general secretary Clyde Puli.
Ms Caruana Galizia had strongly criticised Dr Delia before and after his election as PN leader, raising questions about his financial dealings as a lawyer 15 years ago.
He had denied the claims and sued for libel, but dropped the cases immediately after the murder.