Monaghan is a well known figure in the international TV business with numerous production credits including the Underbelly franchise.
Screentime was acquired by Banijay in late 2012 and Monaghan will step down as executive director at the end of May.
He will continue to consult for the company and will work on development and, in particular, blockbuster miniseries Batavia. The period maritime show was commissioned by Australian free-to-air broadcaster Network Ten.
Screentime cofounder Bob Campbell will remain with the company as managing director.
Monaghan said: “It has been a fantastic eighteen years and I have had the very great fortune of having Bob Campbell as my business partner. It is fair to say that the success of the company far exceeded our initial expectations.
“It has been an extraordinary privilege to work with such a talented and dynamic team, and I am looking forward to watching the company continue to grow under Bob’s leadership, and with the considerable advantage of now being a part of the fast growing Banijay Group.”
Campbell said: “Des and I have enjoyed the closest of professional and personal relationships since we set up Screentime, and I look forward to this continuing.”