Can a B form of a land be cancelled and under what valid reasons

We have one B form land from 50 years , suddenly one issue is takes place here (clearly political issue) , panchayath officials are irritating us , at one time they said that we have the right to cancel your b form . So I want know who has the original right to cancel b form and what are the valid reasons for cancellation. And what are the rights of b form holders.