New Zealand has increased the age for buying alcohol to 20 but kept the drinking age at hotels and bars at 18.

The split drinking age is part of a range of reforms announced by the government.

The proposed laws are designed to tackle teenage drinking and what prime minister John Key describes as a culture of binge drinking.

Eighteen-year-olds will still be permitted to drink in hotels, bars and restaurants but they will not be allowed to buy alcohol from shops and supermarkets until they are 20.

Adults will also face fines of $2,000 for serving alcohol to under-18s unless they have a parent's consent.

The New Zealand government has not, however, moved to lower the blood-alcohol level for driving, which remains at 0.08.