A 64-year-old chiropractor has admitted to using Facebook to post abusive comments about retiring Labor senator Nova Peris.

Chris Nelson has pleaded guilty in a NSW Central Coast court to using a carriage service to cause offence.

Among the comments he posted was: "Go back to the bush and suck on witchity [sic] grubs and yams."

Nelson, who is based at Woy Woy, was arrested at his business in May after making the comments about the Northern Territory Senator, which went viral.

Senator Nova Peris after she announced her departure from politics earlier this year. ( Fairfax Media: Alex Ellinghausen, file photo )

At the time he denied he was responsible, saying his account was hacked, but later made admissions to police.

He showed no emotion during his brief appearance at Woy Woy Local Court.

Outside court Nelson said: "How many times do I have to say 'no comment'?"

In a statement to the ABC, Senator Peris said: "I welcome the news of Mr Nelson's guilty plea".

"Given that the matter is still before the courts and awaiting sentencing, it would be inappropriate for me to comment further at this time," she said.

Court documents reveal the slur that went viral was not the only Facebook post Nelson made to the outgoing senator that day.

His social media accounts have since been shut down but further police investigations found that he posted a second racially abusive message.

The comments included several instances of profanity.

The abuse made reference to Senator Peris' Indigenous heritage.

In his admissions to police, he stated he was not motivated by racism but by government policies on illegal immigration and Aboriginal welfare payments.

He faces a maximum two years in jail and will be sentenced on July 5.

At the time the messages were sent Nelson was the secretary of the Woy Woy (Peninsula) Branch of the Liberal Party.

He was expelled within hours of his arrest.

On her own social media accounts, Senator Peris labelled the comments as "racist and vile hatred".

Earlier this year, Senator Peris announced she would not re-contest her Senate seat at the upcoming election.

After the online abuse was made public, Senator Peris said she would continue to call out and fight racism.

She said no one had the right to make anyone else feel threatened or discriminated against.