He said on one occasion Picasso's wife handed him a cardboard box crammed with sketches and said simply, "Here, this is for you."
But within days of art experts proving the works were genuine, police swooped on Le Guennec and his wife at their home in Mouans Sartoux, near Cannes, in October and arrested them on suspicion of receiving stolen goods.
Police held them both in custody for 24 hours before releasing them without charge, and said an investigation was now under way to establish exactly how the elderly couple came by the paintings.
At his modest, whitewashed villa in the south of France, Mr Le Guennec continued to insist this weekend that he had not stolen the artworks from his former employer.
He said: "I worked for Monsieur and Madame from 1970 to 1973, and for Madame for another three years until 1976 after Monsieur died.
"They both gave me paintings, and on one occasion she gave me a box containing lots of sketches and canvases, perhaps 100 of them, saying 'Here, this is for you.'
"Perhaps they were happy with my work as their electrician and wanted to show their kindness. I don't know.
"I didn't steal them, and am horrified that people think I could of done.
"I didn't really think about what they might be worth. I just put them in a box in the garage and that's where they sat.
"It was only when we were sorting through our things in the summer that I looked through them and thought I'd take them to the Picasso people in Paris and let them know I had them.
"I didn't want my sons arguing over the inheritance and because Picasso was a famous artist I thought they would be better off with his family."
Mr Le Guennec's wife Jacqueline added: "We never intended to sell them, and we wouldn't be living in a house like this if we had intended to make money from these paintings."
The couple's lawyer Evelyne Rees said: "The police thought about charging them with harbouring stolen goods, but they have not done so, because clearly to harbour stolen goods means something must have been stolen. And nothing has been stolen."
Christine Pinault, spokeswoman for Picasso's son Claude, told of the "astonishment" at the Picasso Foundation offices in Paris when Le Guennec arrived with the haul of artworks in a suitcase.
She said: "He made an appointment to come and see us and arrived on September 9 with an unlocked suitcase full of paintings and sketches. We could hardly believe he had simply got on a train with something so valuable.
"He first claimed it was Picasso himself that had given them to him, but he didn't seem to be describe a single occasion when a painting was handed to him.
"When we asked him why he thought Picasso had been so generous, he told us simply that the artist must have thought he deserved them for all his hard work."
Picasso's son Claude and five other relatives of the Spanish-born artist have dismissed Le Guennec's claim that he could have received the paintings as gifts.
Claude Picasso insisted his father would "never" have given such a large quantity of works to anyone.
He told French daily Liberation: "That doesn't stand up. These works were part of his life."
Picasso family lawyer Jean-Jacques Neuer added: "Claude Picasso was astounded. He couldn't believe his eyes.
"Just about everybody has felt that way. When you have 271 Picasso works that were never seen, never inventoried, that's just unprecedented.
"The most important thing is rediscovering important artworks for the good of art history as a whole."
A spokesman for France's Central Office for the Fight against Traffic in Cultural Goods, part of the Interior Ministry, confirmed the paintings had now been seized and were being held in a secure location.
A source told Liberation newspaper: "One mystery among many in this affair is why Mr Le Guennec kept these artworks hidden for such a long time and has only come forward now.
"The works have all been preserved in good condition. They range from notebooks to drawings and completed paintings, including nine cubist paintings which alone are worth some 40 million euros according to experts."
The newly discovered Picassos include a watercolour from his Blue Period, and experts believe nine cubist works in Mr Le Guennec's possession are worth £33 million alone.
Also in the collection are portraits of his first wife Olga, as well as a number of gouaches and lithographs, Liberation reported.