The invention provides a process for the production of a propylene based polymer, said process comprising the following steps: (a) a first polymerization stage comprising homopolymerizing propylene or copolymerizing propylene and at least one α-olefin in the presence of an α-olefin polymerization catalyst whereby to produce a polypropylene component; (b) a second polymerization stage comprising copolymerizing ethylene and at least one α-olefin in the presence of an α-olefin polymerization catalyst whereby to produce an ethylene/α-olefin copolymer component; and (c) blending the polymer components produced in steps (a) and (b) whereby to produce a polymer blend, wherein said first and second polymerization stages are effected in separate polymerization reactors connected in parallel. Also provided are novel polymer compositions comprising: (i) 30 to 97 % by weight, based on the total weight of the polymer composition, of a propylene based polymer; and (ii) 3 to 70 % by weight, preferably 5 to 20 % by weight, based on the total weight of the polymer composition, of an ethylene copolymer plastomer (e.g. an ethylene-propylene plastomer) containing at least 60 % by weight ethylene.