Phthalate free catalyst composition containing a catalyst component obtained by a process comprising the steps of a1) providing a solution of at least a Group 2 metal alkoxy compound (Ax) being the reaction product of a Group 2 metal compound and a monohydric alcohol comprising in addition to the hydroxyl moiety at least one ether moiety optionally in an organic liquid reaction medium; or a2) a solution of at least a Group 2 metal alkoxy compound (Ax') being the reaction product of a Group 2 metal compound and an alcohol mixture of the monohydric alcohol and a monohydric alcohol of formula ROH, optionally in an organic liquid reaction medium; or a3) providing a solution of a mixture of the Group 2 metal alkoxy compound (Ax) and a Group 2 metal alkoxy compound (Bx) being the reaction product of a Group 2 metal compound and the monohydric alcohol, optionally in an organic liquid reaction medium; or a4) providing a solution of Group 2 metal alkoxy compound of formula M n m X 2-n-m or mixture of Group 2 alkoxides M n' X 2-n' and M m' X 2-m', where M is Group 2 metal, X is halogen, R1 and R2 are different alkyl groups of C2 to C16 carbon atoms, and 0 ≤ n < 2, 0 ≤ m < 2 and n+m+(2-n-m) = 2, provided that both n and m ≠ 0, 0 < n' ≤ 2 and 0 < m' ≤ 2; and b) adding said solution from step a) to at least one compound of a transition metal of Group 4 to 6, and c) obtaining the solid catalyst component particles, d) washing said solidified particles, e) recovering the solidified particles of the olefin polymerisation catalyst component, wherein an electron donor is added at any step prior to step c) and is a non-phthalic internal electron donor, and wherein the catalyst component is further modified by a polymeric nucleating agent comprising vinyl compound units. a1) providing a solution of at least a Group 2 metal alkoxy compound (Ax) being the reaction product of a Group 2 metal compound and a monohydric alcohol comprising in addition to the hydroxyl moiety at least one ether moiety optionally in an organic liquid reaction medium; or a2) a solution of at least a Group 2 metal alkoxy compound (Ax') being the reaction product of a Group 2 metal compound and an alcohol mixture of the monohydric alcohol and a monohydric alcohol of formula ROH, optionally in an organic liquid reaction medium; or a3) providing a solution of a mixture of the Group 2 metal alkoxy compound (Ax) and a Group 2 metal alkoxy compound (Bx) being the reaction product of a Group 2 metal compound and the monohydric alcohol, optionally in an organic liquid reaction medium; or a4) providing a solution of Group 2 metal alkoxy compound of formula M n m X 2-n-m or mixture of Group 2 alkoxides M n' X 2-n' and M m' X 2-m', where M is Group 2 metal, X is halogen, R1 and R2 are different alkyl groups of C2 to C16 carbon atoms, and 0 ≤ n < 2, 0 ≤ m < 2 and n+m+(2-n-m) = 2, provided that both n and m ≠ 0, 0 < n' ≤ 2 and 0 < m' ≤ 2; and b) adding said solution from step a) to at least one compound of a transition metal of Group 4 to 6, and c) obtaining the solid catalyst component particles, d) washing said solidified particles, e) recovering the solidified particles of the olefin polymerisation catalyst component, wherein an electron donor is added at any step prior to step c) and is a non-phthalic internal electron donor,