A crackdown on underage boozing in Southland.

Police last night tested 13 of Invercargill's liquor outlets, for compliance with the Sale and Supply of Alcohol Act.

Officers sent a 16-year-old into the stores to try to buy alcohol.

They say his ID was checked by staff at all locations.

However, the date of birth wasn't checked at South City Liquorland, who failed the test.

Sergeant John Harris says it's still a marked improvement on previous operations.

He says it's a timely reminder for all liquor outlets to expect to be tested.