A spy camera has been kept in my house by my neighbour.is it a crime even if i do not register a complaint against my neighbour in the police station?

It depends on jurisdiction. Some localities have personal privacy laws which would enhance the charges of criminal tresspass, breaking and entering, etc. Of course, a crime is a crime whether it is reported or not, just as it is still a crime even if there are no witnesses. The likelihood of succesful prosecutions, however, depends upon citizen reports and credible eyewitnesses. Evidence also helps to convict. If you believe your privacy is being invaded, I would advise you to report this to your police department. If there is any physical evidence, such as the camera someone placed in your home, this would be invaulable to their investigation. I would also take steps to secure my privacy by changing locks, using blinds, and I would inspect my residence if I felt a neighbor was trying to invade my privacy. The best thing I believe you could do for yourself would be to report this to the police, for the deterrent value alone, if for no other reason.