Ahead of this evening's contest versus the Netherlands, Sterling was asked about how the news had been leaked. He said: "I couldn't tell you that. I woke up this morning fuming.
"I had a conversation with Gareth. I hadn't had a conversation with anyone in my agency, so it was a strange one to wake up to."
The 24-year-old Manchester City forward was forced to apologise to his England boss Gareth Southgate.
"The first thing I did after I came off the phone to my agent was see Gareth down the hallway, and I apologised to him for what had happened. I don't know where that's come from.
"[Being captain] that's something that's down to the manager, not for me to decide. But if the manager did do that, it's something I'd be proud and happy to do for sure. That's up to the manager."
Purple PR works on behalf of the player's agent, Colossal Sports Management.
No stranger to controversy in the past, Sterling has more recently been lauded as a positive role model willing to speak his mind. Last year, he appeared in a new campaign for Nike, celebrating his outspoken views on the media and racism in football.
PRWeek approached Purple PR for a comment but had not received a response at the time of publication.