The most commonly used power is under section 317 of the Crimes Act 1961. This section says that the Police, along with anyone the Police require to help, can enter your place without a warrant, with force if necessary, in any of the following situations
•when the Police have found you committing an offence punishable by a prison term and are freshly pursuing you
•when the Police have good cause to suspect that at your place you’ve committed an offence punishable by a prison term
•when it’s necessary to stop an offence being committed that’s likely to cause immediate and serious injury to any person or property.
If the Police officer isn’t in uniform, you can require them to produce identification before they can enter your place.