Candidates Steps Down Or Doesn't Join The Organisation Even After Accepting The Offer

Hi
Recently we have seen that candidates steps down or doesn't join the organisation even after accepting the offer.We have also noticed that candidates dont even bother inform that they are not interested in joining due to which the employer & the consultancy both have to suffer .
Experts pls suggest on the same how can we avoid this
Thanks in Advance
Amruta

Recruitment process is at fault. The recruiter/selector fail to understand that candidate will join or not. So need to review the competency of interviewer / selector.