WELLINGTON (AFP) - Dildo throwing is not a good look for New Zealand and an "appalling way" to behave on the country's national day, Prime Minister John Key said on Saturday (Feb 6), angered by an attack on a senior government minister.

Economic Development Minister Steven Joyce was hit in the face by a pink dildo thrown at him by a protester during national day celebrations in the northern town of Waitangi on Friday.

"It's appalling because that image has gone around the world and there are now people in countries all over the world saying the way New Zealanders theoretically commemorate or celebrate their national day is with a senior politician having a sex toy thrown at them," Mr Key said.

"That's the way now that people from overseas are viewing how we have a celebration on our national day. It just isn't the right image for New Zealand."

Mr Key added that the protest was "crude and basic" on what should be a family occasion.

Waitangi is traditionally the centre of New Zealand's national day as the town where the Treaty of Waitangi was signed between the British Crown and indigenous Maori in 1840, paving the way for European colonisation.

However, celebrations are often marred by protests, with Mr Key refusing to attend this year because of fears of violence.