Mr Davis has left the firm “by mutual agreement”.
He has been replaced, in an interim basis, by Stephen Jones.
Mr Jones, who joined the business in 2002, is currently chief investment officer for Aegon Asset Management (AAM) Europe and Kames Capital, and he will take on the interim CEO responsibilities while continuing with his current role.
Prior to becoming the CIO at Kames in 2013, Mr Jones was joint head of fixed income.
The company also confirmed that Bas NieuweWeme AAM’s global CEO will take over Mr Davis’ responsibilities as head of AAM Europe also on an interim basis.
A Kames Capital spokeswoman said: “We would like to thank Martin for his contribution to the business during the last six years and wish him every success with his future career.”