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Three out of four New Zealanders believe the upcoming "anti-smacking" referendum is a waste of money, a survey has found.

The Research New Zealand poll of 481 people found 77 per cent didn't support spending money on the non-binding referendum which will cost $8.9m.

Eighteen per cent felt it was a good use of taxpayer dollars, while five per cent were unsure.

Prime Minister John Key has said the Government is unlikely to change the law, regardless of the result of the referendum.

Research New Zealand director Emanuel Kalafatelis said New Zealanders appeared reluctant to spend so much on a referendum during a recession.

"Despite widespread protest about the so-called 'anti-smacking bill', it seems Kiwis aren't willing to spend millions of taxpayers' dollars on a referendum."

He said it would be interesting to see how opinions on the cost translated to voter numbers.

Of all the demographic differences in the poll, the only significant difference was between the sexes.

Eighty per cent of female respondents believed the referendum was a waste of money, compared with 70 per cent of male respondents.

The non-binding, citizens-initiated referendum will be held by postal ballot from July 31 to August 21.