It's being suggested a $20 minimum wage in 2021, is the same as a $17.50 minimum wage today.

Economist, Dr Eric Crampton of the New Zealand Initiative think tank, told Mike Hosking there are already good numbers from MBIE around the effects of minimum wage increases.

He said if today's minimum wage was $17.50, it would cost jobs and the country.

"That would be about 15,000 fewer jobs than we would otherwise have and a net cost to the government of about $125 million."

LISTEN ABOVE AS ERIC CRAMPTON SPEAKS WITH MIKE HOSKING