A war of words has erupted over National MP Todd McClay's proposed gang patch ban, with Mana Party leader Hone Harawira labelling him a "foolish dickhead" promoting a "deeply racist" bill.

Harawira has threatened to wear a gang patch into Parliament if the bill becomes law, a move McClay says casts doubts on Harawira's suitability to be an MP.

"The guy is such an idiot," Harawira said. "I'm not going to stand by and watch a blonde, blue-eyed redneck kick around poor people who, out of desperation, bond together because they see nothing in the blonde, blue-eyed society to give them a sense of hope for their own or their children's futures."

Harawira said he was "not a great lover of gangs" but said McClay's pledge that government agencies would not deal with anyone wearing a patch, and that police would want to talk to them about criminal behaviour, was nonsense.

"The fact of the matter is that this foolish dickhead doesn't know what's going to happen. The police aren't interested in this. It's not going to be deep-blonde white-boy Todd that's going to be affected, it's going to be those working in the agencies."

McClay's Prohibition of Gang Insignia in Government Premise bill has yet to pass its first reading in Parliament, but is expected to do so. If it became law, offenders could face a fine of up to $2000. Police would also have the right to confiscate and destroy patches and insignia.

MPs vote in two weeks whether to send it to the select committee phase, and McClay says he has the numbers for that.

Labour, the Greens and Mana all oppose the bill. Harawira says that if it became law he would consider wearing a patch to Parliament, a stance McClay described as an embarrassment to the Te Tai Tokerau MP and his Mana movement.

"Harawira's defence of gang membership is shameful," McClay said. "He has told gang members to disregard any law, by saying he is considering wearing a patch to Parliament in protest. Many people would question whether views like that have any place in Parliament.

"He needs to join the real world and do something about the harm and intimidation of gangs, rather than being an apologist. Through his actions he's endorsing the misery inflicted by drug dealers and murderers, and supporting a group that's preying on the vulnerable."

But he said he was disappointed the attacks had become personal. "He may say he is not pro-gang, but his comments will lead many to think otherwise."

Harawira said he understood why some people from lower socio-economic backgrounds joined gangs, adding that 90 per cent of those targeted by the bill would be Maori, making it a "deeply racist piece of legislation".

"The man [McClay] is so disconnected from reality that he's inflicting on one sector of society, crimes that are from right across it. Anybody who thinks gangs are the only ones involved in drugs is an absolute bloody fool. He wouldn't know a gang if it kicked him in the nuts."