Fewer than 50 per cent of New Zealanders voted for a new flag design - but Prime Minister John Key believes there is support for change.

Key, speaking to the Herald just before he went into to chat to Newstalk ZB's Leighton Smith, said the issue was important for the country.

"I don't think it's a legacy project for me, I think it's an important issue for New Zealand."

Key was speaking the day after official results showed Kyle Lockwood's silver fern flag with black, white and blue won the first round of the flag referendum.