Phillip Schofield admitted on Friday to having an affair with a younger man who worked on This Morning.
In response to Schofield's statement to the Daily Mail, his agents at YMU Group said they had dropped the presenter.
And ITV later said they were "deeply disappointed by the admissions of deceit" by one of their biggest stars.
In his statement, Schofield said: "I am making this statement via the Daily Mail to whom I have already apologised personally for misleading, through my lawyer who I also misled, about a story which they wanted to write about me a few days ago."
The statement added: "The first thing I want to say is: I am deeply sorry for having lied to them, and to many others about a relationship that I had with someone working on This Morning.
"I did have a consensual on-off relationship with a younger male colleague at This Morning.
"Contrary to speculation, whilst I met the man when he was a teenager and was asked to help him to get into television, it was only after he started to work on the show that it became more than just a friendship. That relationship was unwise, but not illegal. It is now over.
"When I chose to come out I did so entirely for my own wellbeing. Nobody 'forced' me out. Neither I nor anyone else, to my knowledge, has ever issued an injunction, super or otherwise, about my relationship with this colleague, he was never moved on or sacked by or because of me.
"In an effort to protect my ex-colleague I haven't been truthful about the relationship. But my recent, unrelated, departure from This Morning fuelled speculation and raised questions which have been impacting him, so for his sake it is important for me to be honest now."
Schofield continued: "I am painfully conscious that I have lied to my employers at ITV, to my colleagues and friends, to my agents, to the media and therefore the public and most importantly of all to my family. I am so very, very sorry, as I am for having been unfaithful to my wife.
"I have therefore decided to step down from the British Soap Awards, my last public commitment, and am resigning from ITV with immediate effect expressing my immense gratitude to them for all the amazing opportunities that they have given me. I will reflect on my very bad judgement in both participating in the relationship and then lying about it.
"To protect his privacy, I am not naming this individual and my deepest wish is that both he and his family can now move on with their lives free from further intrusion, and that this statement will enable them to do so. I ask the media now to respect their privacy. They have done nothing wrong, and I ask that their privacy should be respected."
Meanwhile, Schofield's agent released the following statement: "Honesty and integrity are core values for YMU's whole business, defining everything we do," Mary Bekhait, the group CEO of YMU Group, said.
"Talent management is a relationship based entirely on trust.
"This week, we have learned important new information about our client Phillip Schofield. These facts contradicted what Phillip had previously told YMU, as well as the external advisors we had brought in to support him.
"As a result, on Thursday we agreed to part company with Phillip, with immediate effect."
An ITV spokesperson later said: "We are deeply disappointed by the admissions of deceit made tonight by Phillip Schofield.
"The relationships we have with those we work with are based on trust. Phillip made assurances to us which he now acknowledges were untrue and we feel badly let down.
"We accept his resignation from ITV and therefore can confirm that he will not be appearing on ITV as had previously been stated."