Paul Smalley has left Pompey with immediate effect.
The head of youth operations yesterday came to a mutual agreement with the Blues to depart the role he has occupied since July 2009.
Smalley was appointed following Paul Hart's elevation from the position to first-team manager on a permanent basis.
The 44-year-old Smalley had previously worked as a technical director with the New Zealand FA.
Pompey will now seek to recruit a replacement.