They have been tested by ROSPA and Which magazine & have been pronounced 'unsafe' and should not be used ...........................
Far from offering the intended protection, plug protectors can, in fact, increase the risk of electric shock and fire hazards. Organisations including The Royal Society for the Prevention of Accidents (RoSPA) and the NHS both advise against them.
To understand why they're dangerous, you first have to understand how sockets work.
British 13-amp plug sockets are designed to be safe. They have plastic barriers, which slide into place when the socket is empty, essentially creating a block between the electrical current and any small fingers trying to poke their way in. When a plug is inserted, the earth pin moves the barrier, and whatever device you're powering gets electricity.
One of the only other things that can easily move the safety barrier out of the way is something the size and shape of a normal plug – for example, a plastic plug protector.
When these are inserted in the socket, it leaves the circuit open, increasing the risk of electric shocks. What's more worrying is that these protectors can be inserted upside down, or easily snapped in half to allow even easier access to the electric current.
In a nutshell, by using a plug protector, you are basically undoing all of the safety features inherent in a UK socket. Not only are you risking causing shocks or starting an electrical fire, but also melting and damaging the socket itself.
Even the IET and the PAT testing organisation say they 'do more harm than good'
2012 44 Autumn Wiring Matters
Socket Covers - Safety Advice