National's Tau Henare has "overstepped the line" by calling Hone Harawira "so racist, he has chocolate milk in his cup of tea," a fellow MP says.



Henare - who has been dubbed the Minister of Twitter for his prolific use of the social networking site - posted the comment on his Twitter account earlier this afternoon.



He addressed the remark to Social Development Minister Paula Bennett - but spelt her name wrong. Although Bennett set up an account, she does not use it.



Her spokeswoman said she had not seen the message.



It's unclear what sparked the taunt - neither Henare nor Harawira were answering their phones this afternoon.



Labour MP Trevor Mallard, also an enthusiastic social media user, said "it's beyond the limits."



"The line is drawn in a different place on Twitter, but in this case Tau has gone beyond it. It's unlikely to upset many people, mainly because of the way that Hone is perceived by a lot of people.



"Some people will see it as Hone getting a bit of his own back. If it was said about anyone else it would be regarded much more negatively."



It's not the first time Henare has made a dig at Harawira. Last year Harawira said he would not feel comfortable if one his children dated a Pakeha - Henare said his comments were "racist and stupid."



"It's like watching the ugly end of a relationship that's been breaking down for some time," Mallard said.



Prime Minister John Key refused to comment.