He succeeds Keith Grainger, who is now the SRU's commercial director.
David said: "I am delighted to be able to advise that I have taken over the tournament director's position from Keith Grainger on an interim basis until the end of the season, at which time a permanent successor will be appointed.
"My first task is to thank Keith for all his hard work in establishing the Celtic League and Cup into the strong competitions that they have become. The fact that Ireland and Wales sit top of the Six Nations emphasises just how competitive our tournaments are.
"Having been a participant in these tournaments I am well aware of some of the issues that require to be developed to drive the Celtic League forward. Of particular necessity is to have stability and consistency applied to all aspects of our tournaments."