Retailers are being warned to be on high alert after police received a number of complaints about counterfeit money being used in stores around the North Island.

The notes have been $20, $50 and $100 denominations.

Police are warning retailers to keep their eyes peeled for counterfeit bank notes this Easter.

Police say typically the offenders have gone into shops and supermarkets, purchased a small item using a large denomination note and then received legitimate cash as change.

Senior Sergeant Simon King says retailers should be alert to this practice, especially over the busy Easter weekend.

For information to help identify counterfeit notes, people can go to the Reserve Bank of New Zealand website and look under "notes and coins" where they will find information on how to spot a counterfeit (www.rbnz.govt.nz).

'If retailers are suspicious about cash being used in their shops, they should take the following action: Consider refusing to accept the note, record the description of the person offering it, record the number plate and description of any vehicles used by the person, call Police on either their local number or 111, preferably while the person is still in or near the shop,” says Simon.

'Retailers should also consider their own safety first when dealing with such people.”

Any suspicious behaviour should be reported to your nearest police station.

Alternatively, information can be left anonymously via the Crimestoppers 0800 555 111 line.