One of New Zealand's top legal minds is backing a suggestion that shoplifters and people ripping off retailers should be given spot fines.

Retail New Zealand argues issuing infringement notices would stop the chain of crime, believed to cost up to $1 billion a year, before it escalates and free up court time.

It says for repeat offenders, or anyone part of a criminal gang, there should be stronger penalties, like prison.

AUT Criminal Law Professor Warren Brookbanks said fines could definitely be one tool to tackle lower-level retail crime.

"Any prosecution takes up a lot of police time in getting witness statements and so forth, and all the court time involved. Any system which took pressure off the courts would be a good thing."

"The idea of infringement notices would be effective for first-time offenders because of the deterrent affect, especially if there was quick and swift action."

Professor Brookbanks said you'd need different measures for more serious crimes, like violence and threats against shopkeepers.

He said it could work in the way traffic fines do.