Returns Policy Makro Cornubia

I tried to take back a Cordless vacuum cleaner I bought less than 6 months ago as it has stopped working properly. I am told that they have to send it off for an assessment for customer negligence before they return / refund / replace. This can take up to 21 working days (before Christmas). How is this a fair policy? Where in the consumer protection act does it state that an assessment for customer negligence is necessary for a defective product to be returned? Where does it state this when you purchase the product? It was like banging my head against a brick wall. I will not be purchasing anything else from makro if this is the policy. Disgraceful customer experience! I was told I could seek my own legal advice if I wanted to, by manager.