I am pretty sure this is incorrect advice being given by the people above.
I have a BMW 1000cc bike which ONLY has a rear numberplate. I go through Cantt checkposts every single day, and they just look at the back plate and go that's fine. So that's police and MPs.
Have been stopped by a traffic cop as well, and again he went around to the back looked at the numberplate, asked for a license and papers, talked to me for 15 min. tried to find anything wrong, never mentioned the front plate or implied that I need to have one.
So not sure about smaller bikes, but certainly for the larger bikes the front plate is NOT a requirement.
The way my bike is made, it would be almost impossible to fit a front numberplate anyway.