The Argentine, whose contract expires on June 30, decided to share his thoughts publicly and in detail, before announcing he would be leaving the club.
"This is first time in my career that I have spoken out like this and it makes me sad," he said in a video posted on his social networks.
"When I say campaign, I mean people at the club have tried to discredit me as a professional and as a person."
Garay then went on to explain why he chose to go public with his disgruntlements, particularly in reference to his contract.
"All of this started when it was leaked that I had rejected an offer of 2.7 million [euros per season] and that's totally untrue," he stated.
"They said I didn't want to stay at the club which was not true either.
"On July 2, I was offered a contract notably inferior of the one I already had.
"In August, instabilities started to show like with the case of [former coach] Marcelino so I decided to wait until everything blew over to discuss a contract renewal.
"On November 13, a verbal contract was agreed but nothing in writing, until I met another of the club's representatives in January where conditions had changed.
"I still wanted to renew with the club but on February 1, I injured my knee and required surgery.
"A little after that I was asked to go on sick leave, I asked again about my contract renewal but I was met with silence."
Garay added that he volunteered to have his wages cut amid the coronavirus crisis but the club felt it wasn't enough.
"From the beginning, I wanted to cooperate and be furloughed which would have resulted in the reduction of my wages but the club didn't accept, they wanted me to have an even bigger reduction because I was already on sick leave," he revealed.
"I want and have always wanted to stay at the club because Valencia have given me the opportunity to overcome challenges; meet amazing people and experience the highs and lows with the fans.
"I have been happy here and would love to continue but it's not up to me unfortunately."
The former Real Madrid man closed by announcing that his future with the club was over.
"My farewell comes straight from the heart, because I believe I am a good man and I believe that you deserve to know the truth," he stated.
"When you see that things that are happening are hurting people around you like your family it hurts you too, especially when your children ask you why you are sad, Its hard to give them an answer.
"I want to finish saying that lies are easy to believe but unfortunately the truth has to come out at some point and with that, I bid you farewell and 'Amunt Valencia'."