The present invention discloses a method for preparing an heterogeniseded catalyst component comprising the steps of: a) providing a halogenated precursor component of formula (I) --X--[--CH.sub.2]--CH.sub.3 b) reacting the halogenated precursor with an ionic liquid precursor in a solvent to prepare an ionic liquid; IL.sup.+X.sup.- c) optionally, reacting the intermediate IL.sup.+X.sup.- with a salt C.sup.+A.sup.-, wherein C.sup.+ is a cation that can be selected from K.sup.+, Na.sup.+, NH4.sup.+, and A.sup.- is an anion that can be selected from PF.sub.6.sup.-, SbF.sub.6.sup.-, BF.sub.4.sup.-, (CF.sub.3--SO.sub.2).sub.2N.sup.-CIO.sub.4--, CF.sub.3SO.sub.3.sup.-, NO.sub.3-- or CF.sub.3CO.sub.2.sup.-. d) using the ionic liquid prepared in step b) to heterogenise a metallocene component of formula (II) R''(CpR.sup.m)(Cp'R.sup.n)MQ.sub.2 wherein Cp and C'p are independently selected from substituted or unsubstituted cyclopentadienyl groups M is a metal selected from Group 4 of the Periodic Table, R'' is a structural bridge imparting stereorigidity between Cp and Cp' and Q is a halogen or an alkyl having from 1 to 12 carbon atoms; e) heterogenising the ionic liquid/metal system by addition of an apolar solvent inducing the precipitation reaction; f) retrieving a metallocene catalyst component heterogenised by an ionic liquid. It also discloses an active catalyst system hetero genised by an ionic liquid and its use in the polymerisation of olefins.