A spokesman for Sharples said Cooper was no longer working at the electorate office.
Offensive text messages have also emerged from a phone listed as "emergency" contact for Sharples' Tamaki-Makarau electorate office.
The phone was used by Cooper and was the number on which the Herald on Sunday reached him last Thursday.
The messages were sent to Jamie Lockett, who was moved out of the building when Black Power moved back in. Lockett had approached Cooper wanting his property back and was texted: "w***, w*** ... you do too much w***ing".
In another message, Lockett was invited to "get ur boxing gloves on an get down da pad". The text message stated Locket would be matched with "one of da prospects" - someone who has to prove themselves to join a gang.
A spokesperson for Sharples said: "Dr Sharples has stood Martin down from work at his electorate office, and asked [Parliamentary Service] to conduct an independent investigation into allegations made against Martin. He hopes all matters can be cleared up soon.
"If you have information that you think is relevant, including the text messages, you should forward it to Parliamentary Service. Beyond that, it would be inappropriate for Dr Sharples to comment on an employment matter while an active investigation is underway."