Their research highlighted the fact that 90% of the lights they tested did not meet UK safety standards, it's illegal to sell them in this country and they are genuine safety risk.
Worryingly for you and your family, several sets were found to be a fire or electrocution hazard with the Which? report highlighting a host of potentially very dangerous problems.
These included control boxes becoming so hot that they started to smoke and then melted leading to a 'charred and molten mess' and an obvious fire hazard.
Circuit boards were found to be incorrectly wired and poorly insulated with cables shoddily fitted so they became easily detached.
All these deficiencies could result in you or your children receiving a nasty shock.
What should you look out for?
Packaging for a start is a giveaway, some cheap lights will arrive with poor packaging or none at all.
Manufacturers are obliged to provide clear instructions as to how the lights should be fitted and where they should be used, so if these are missing it's another bad sign.
All light sets should have CE mark indicating they conform to health, safety and environmental protection standards. A further WEEE symbol means the product is recyclable.
So the implication is to shop from an established UK retailer who sells well known branded products that have been thoroughly tested and meet all EU safety standards
On GardenSite all our Christmas lights and seasonal electrical products are from leading European suppliers including Konstsmide, Lumineo and Premier Decorations, so you can be assured that your Christmas will be bright, colourful and, most important of all, very safe.