Houllier said: "I want to stress Ian has not arrived here on a lifeboat or on some kind of rescue mission. This is something I wanted for a long time.
"The manner the news was leaked in was unfortunate because I wanted to wait for the right time to announce this.
"It was important for my staff, the chief executive and chairman to know exactly what the situation was, but as it turns out, because of other commitments, Ian won't be able to begin properly until the end of January.
"I am pleased he accepted the role because of the young and say inexperienced strikers we have.
"Phil Thompson has done a great job with the defenders, Sammy Lee with the midfield and now Rushie will help our strikers."