Haug announced last week that he will be stepping down from his role at the end of this month after 22 years in charge of the German car manufacturer's motor racing activities.
Speaking at length for the first time since news of his departure was made public, Haug said Mercedes' tally of just one win from three years in F1 cost him his job.
"This was a decision made after the last race," he told AUTOSPORT. "We had a report in Stuttgart and we reached a mutual agreement that we split. I take the responsibility for not having been successful enough in three years.
"We were quite OK with our pace in the first third of the season - but then we dropped back. So we need changes, and I fully accept that.
"There is no bad feeling between the board and I. We are splitting amicably and we have found a good solution for both sides."
He added: "We should have done a better job. We changed to the 60 per cent windtunnel in the middle of the year; we suffered a little bit with the RRA [Resource Restriction Agreement] and personnel numbers, but I don't want to have any excuses. My job was not good enough.
"I take full responsibility for that. Even if I don't build the car, I am in charge. And if I was responsible for the victory in China, I also have to be responsible for everything else that happened."
Haug has no immediate plans once his current commitments with Mercedes-Benz are over, and will only make a decision next year.
"I will still be involved in the first quarter of the year, and then I am a free agent. I have no thoughts on what I will do – but things will settle down.
"I am happy to have some time for skiing in the first part of the year, and my friends called me and say it is great I have the time now. This year I was away for 34 weekends out of 38 between February and the final race, which is quite a lot."
Regarding the possibility of a restructuring at Mercedes, or a replacement being lined up, Haug said: "I do not know about that. It is not my position to judge that, and this will be done by the board."
Haug is sure, however, that Mercedes will be able to achieve its target of more wins and title success in the future.
"I am 100 per cent convinced of that," he said. "It takes time and we should be further down the road than we are, but I think the guys will be fine.
"We will not be the world beaters in the first step, but I am sure Niki [Lauda] and Ross [Brawn] will give it everything. I will support them, and should there be any need for further discussions or, advice, they can always contact me – but they are responsible."