Three clients accused of charges and out on bail have reported late to the police station and been told to give a DNA sample voluntarily or face arrest, a South Auckland lawyer says.

Lawyer Shane Tait mostly works at the District Court in Manukau and said he knew of three cases where clients had been pressured into giving DNA samples.

"If they had reported late then the Constable would say: Look, give me a sample of your blood and I won't arrest you for the bail breach," Mr Tait said.

He said he has written to the police DNA data bank and asked them to destroy samples on the grounds that they had not been taken with permission.

His comments come after Maori Party MP Hone Harawira said he had heard of cases where young Maori were being "conned" by police into providing samples when they hadn't committed any crime.

"One young Maori told me the police wanted the sample because one of their relatives 'might be known' to the police," Mr Harawira said.

He accused police of using Nazi-style tactics and wanted them to desist or he would advise the young people in question to engage a lawyer and sue.

Police can currently collect voluntary DNA samples only from people over 14 under strict guidelines when investigating a crime scene, but those guidelines will be relaxed from next month, meaning people aged 14 to 17 can be required to give samples under strict conditions if they face charges.

Mr Tait said as the law stands, police cannot force people to give a DNA sample unless they have a High Court order.

However, Mr Tait said unfortunately, people do not know their rights.

Mr Harawira said until Police Minister Judith Collins could give an assurance that police had been "pulled into line" he would recommend that all young Maori refuse to give voluntary DNA samples.

Ms Collins and Police Commissioner Howard Broad told Radio New Zealand the law was clear and people should simply stick to it.

"I would suggest that people do comply with the law around DNA samples and not break the law based on what an MP happens to have said," Ms Collins said. "I am very sorry that any comment has been made around so-called Nazi-style behaviour - that is not New Zealand police."

Mr Broad said if Mr Harawira thought he had a genuine case he needed to make a complaint, "and we will deal with it".

He said the law around collecting samples from young people was quite clear.

"I would imagine that will be very easily cleared up."