The NSW Labor member for Wallsend, Sonia Hornery, has been charged by the NSW Electoral Commission for misusing information on the electoral roll.
Wallsend is an electorate that covers a large section of western Newcastle.
The commission alleged that in August 2016, Hornery used her position to access enrolment information that had been provided to the Labor Party.
The ABC understands the matter relates to an argument the politician was involved in on Twitter after former premier Mike Baird announced he was going to ban greyhound racing in NSW.
Hornery is alleged to have used the electoral roll to look up the details of the person with whom she was arguing.
The ABC has been told she wanted to take the argument "offline" and wrote them a letter explaining why she backed the Labor Party's opposition to the ban.
Hornery released a statement saying she would "vigorously" defend herself.
"I take my duties as an MP very seriously and always act with integrity," she said.
"As the issue is about to go to court, I don't think it appropriate to make any further comment until the process is complete."
The offence carries a maximum penalty of $110,000 but as the matter would be heard in a local court, the maximum fine that could be imposed is $22,000.
