Discussing the run-up to his departure, Gallas wrote: "Milan were knocking on my door. An irony really, this prestigious Italian team were offering me a salary higher than that which I was asking of Chelsea.
"Straightaway, I was seduced. Not because of the euros but because of the faith a club has in you, the value they put on you.
"The club (Chelsea) came back to me and said: 'Weâ€™ll offer you a new contract with a rise but not as much as youâ€™re asking'. Peter Kenyon, the chief executive, was against satisfying my demands. He made our life hell.
"'I donâ€™t think either the owners or Kenyon were aware of my contacts with Milan. We let them know and told them of the offer, which was superior to their own and what I was demanding of Chelsea. They wouldnâ€™t stump up.
"Chelsea said, for their part, that they wanted to keep me and their offer was still open. No one knows how laughable their offer was and what I deserved."
In an attempt to explain how Chelsea reached the conclusion he would be prepared to score an own goal if forced to stay, Gallas divulged the details of a conversation he had with then manager Jose Mourinho.
"You know, when I play for a club, I need to play with heart. Chelseaâ€™s owners have disappointed me, they have not realised what Iâ€™m worth.
'Itâ€™s taken time, the negotiations. Iâ€™ve just come to the point where my heart is no longer at Chelsea.
"Youâ€™re going to put me on the pitch OK, but if the heart is not there and Iâ€™m not concentrating, I risk making errors, errors that Iâ€™m not used to making. We could let in a goal, so lose a match stupidly. This is what I said, word for word,â€™ wrote Gallas.
"I declared that I wanted to go. That conversation would have an absolutely incredible effect in the media a few weeks later."
Referring again to the "own goal" claim, Gallas continued: "I would have been incapable of such utter monstrosities. No player, ever, whoever he was, could say or think he would score an own goal. It isnâ€™t done."
He added: "My first match for Arsenal against Chelsea was very difficult. Chelseaâ€™s supporters whistled me every time I got the ball; they really had it in for me. For them, I was a player who would score an own goal, they ignored the truth. I was gutted."