A criminal offence in many countries. In Britain the offence is spelt out out in section 5, sub-section 2 of the Criminal Law Act 1967:
2) Where a person causes any wasteful employment of the Police by knowingly making to any person a false report intending to show that an offence has been committed, or to give rise to apprehension of the safety of any persons or property, or intending to show that he has information material to any Police enquiry, he should be liable ………
A prosecution can only take place with the consent of the Director of Public Prosecutions. A fixed fine of £80 can be applied in the courts, regardless of how much time has been wasted.

£80 is however small beer to the amount of time and money the local constabulary would have to invest in investigating a crime. A call-out that requires police officers to travel to a location, take statements from witnesses could take up several hours of police work. If the coppers haven't yet cottoned on to the fact they are working off false or misleading information, and they may then be obliged to take a suspect into custody, and book, gaol and interview them. The total police time involved could be substantial. Even more resouces could be wasted if a false report required police to look for a missing child in a large dense forest.

In New Zealand, community service orders have been placed on individuals found guilty of wasting police time.