Employer has own policies - changed all the method of bonus and start giving according their own policies

I am working in a Production Company as a HR manager but my employer make their own policies except the law Eg: when the time came to distribution of Bonus he changed all the method of bonus and start giving according their own policies which is not seems fair.
Please suggest me what I supposed to do and How I deal with them to do right way because this our right.

Dear Jyoti :
From your post it seems your employer is following labour laws and for other points they do it as per company specific policies.
by bonus, if you mean statutory bonus it has to be as per bonus act but for bonus amount other than statutory bonus company can distribute as per their policies or as per agreement with labour unions if any.