If you are talking about the FARs under the FAA system, then you are required to have a safety pilot and you are both entitled to log PIC for the time the manipulator of the controls is under the hood.
That's interesting, didn't know that was the case on the other side of the pond. Who is then the person responsible for the safe conduct of the flight? Does the safety pilot have to be a CFI or just another PPL holder?
Ciao,
Dg800