Last September, a video showing him apparently bribing an opposition Congressman set in train his own and Mr Fujimori's downfall.
Mr Montesinos, who was hauled back to Peru on Monday after eight months on the run, made the claim as he met six anti-corruption judges sorting out the many charges against him.
The former head of Peru's National Intelligence Service (SIN) said he had video tapes of meetings with businessmen, diplomats and politicians going back to 1990.
Last September, a video showing him apparently bribing an opposition Congressman set in train his own and Mr Fujimori's downfall.
Since then hundreds more videos have been recovered, showing Mr Montesinos or subordinates paying off election officials, military chiefs and businessmen as part of a web of corruption which kept Mr Fujimori in power.
'Acting on orders'
According to Peruvian newspapers, Mr Montesinos also claimed he recorded the videos on Mr Fujimori's orders, and that the former president wanted to be kept informed of all SIN affairs.
Some analysts think Mr Montesinos' defence to the charges against him will be to argue he was merely following orders.
Mr Montesinos faces 52 charges, although these are likely to be simplified into separate fields such as drug trafficking, arms dealing and human rights violations.
"It is a wide range of crimes that practically covers the majority of the penal code," said Jose Ugaz, appointed to investigate Mr Montesinos.
It could be months before the case reaches court.
Fears for life
Mr Montesinos, who is being held in the Justice Ministry, is battling to avoid being transferred to Lima's maximum-security naval prison.
Apparently he is frightened to be put under the control of military leaders who may want him silenced.
Trinidad Becerra, Mr Montesinos' wife, said he would go on hunger strike if moved to the naval prison.
"His health could be in danger, his life, who will take responsibility for it?" she said.