Ocampo, who was taken to a local police station, told Reuters the charges were an attempt by the government to exclude leftwing groups from mainstream politics and prevent them from seeking re-election in congressional elections on May 14.
The former journalist said: "These charges of murder are political harassment and repression and are an attempt to prohibit me from campaigning."
He has said he was in prison when the NPA started killing suspected government spies.
Marcos era killings
Ocampo was forced to go underground with the communist fighters when Ferdinand Marcos, the late Philippines leader, declared martial law in 1972.
Captured in 1976, he was tried in a military court and detained until 1985 when he escaped and rejoined the armed group.
"These charges of murder are political harassment and repression and are an attempt to prohibit me from campaigning"
Satur Ocampo, Philippines legislator
Re-arrested two years later, Ocampo was freed in 1992 when the government opened peace talks with the communists. He won a seat in congress in 2001 as a member of the Bayan Muna (Nation First) party-list group.
The government views Bayan Muna and other leftwing groups as NPA fronts and has accused Ocampo and other legislators of helping to fund one of the world's longest-running communist insurgencies, which has killed more than 40,000 people since 1969.
Leftwing groups deny the allegations and accuse the military of killing hundreds of their members in extrajudicial executions. The armed forces blame the murders on internal purges in the communist movement.
Gloria Arroyo, the president, sees the NPA as the Philippines' biggest security threat. Last year she declared all-out war on the group, which is largely based in rural areas and engages the police and military in deadly tit-for-tat battles.
Peace talks collapsed in 2004 when Washington and some European states put the NPA on terrorism blacklists. The group has more than 7,000 fighters and is active in 69 of 81 provinces.