Researchers calling for a 'salt tax' say it could add years of life to thousands of people and save the country millions of dollars.

A study by researchers at Otago University's Wellington Campus looks at eight interventions to lower dietary salt by a third over several years.

Professor Nick Wilson says introducing a 'salt tax' was the second best strategy behind regulation with food industry cooperation.

"It actually gains revenue up to four hundred and fifty million a year for the government which could be ploughed into healthy meals for kids at school or subsidies on fruit and vegetables."

If the Government introduces regulations, then industry is much more likely to be cooperative, Wilson says.

"Voluntary measures are much slower and industry has problems when some companies move and others don't. If it's a level playing field and the government sets maximum levels industry should be reasonably happy."

Professor Wilson believes its a very easy tax in theory to implement because there is just one salt producer in the country.