A retired French secret service agent who says he planted the bombs 30 years ago which sank a Greenpeace ship and killed a photographer has apologized.

Jean-Luc Kister told Television New Zealand that he and his colleagues never meant to kill anybody when they attached two bombs to the Rainbow Warrior on July 10, 1985, while the boat was moored in Auckland.

The boat was due to travel to French Polynesia to protest French nuclear testing. The bombing killed 35-year-old photographer Fernando Pereira, who drowned.

Kister says the death has plagued his conscience ever since. He described the operation as a "big, big failure."

Greenpeace New Zealand's executive director Bunny McDiarmid says it is good to hear the apology but she believes the French agents acted recklessly.