Former National MP Jami-Lee Ross has accused a National Party staffer of taking advantage of his elderly grandmother by forging a relationship with her without telling her family or making clear she was a National staffer.

Ross is so incensed he has lawyered up and written to Parliamentary Services, the staffer's employer, complaining about it.

But Newshub has been given a text Ross - now an Independent MP - sent to the National Party staffer 10 months ago, thanking her for supporting his grandmother.

The letter of complaint comes after last year's high-profile political blow-up between Ross and National, during which time Ross claimed Simon Bridges was a "corrupt" politician.

Ross now claims a National Party staffer has been "harassing" his elderly grandmother, who "felt she was being used" to get to Ross.

"She's a vulnerable person," Ross told Newshub.

The letter of complaint



Ross has hired prominent lawyer Graeme Edgeler to write a letter to Parliamentary Service, who employs the staffer, raising "a matter of serious concern".

The letter calls on Parliamentary Services to stop the staffer from contacting Ross' grandmother.

"Mr Ross knew [the staff member] during his time as a National MP, and has recently become aware that [the staff member] has been visiting his property in his absence and has sought to expand her acquaintance with Mr Ross's elderly grandmother into regular contact," the letter says.

"This seems to Mr Ross to be a calculated attempt to invade his and his family's privacy."

The grandma's account



Ross' grandmother told Newshub she didn't know the staffer worked for National, and that it "really hurt" finding that out last week.

She says she was "disgusted and upset" to find that out.

The National Party staffer



Speaking through a National Party spokesperson, the staffer says she only picked up Ross' grandmother - she calls her 'nana' - once from outside the house, didn't go on the property and hadn't timed it for when Ross was out.

She insists she did tell Ross's grandmother she worked for National.

Ross said he hasn't spoken to the staffer since the fall-out with the National Party, and that he hasn't had contact with her at all.

But after Newshub's interview with Ross, National showed Newshub a text Ross sent the staffer last November, just a month after he left National.

The text message



The text message National showed Newshub from Ross shows he acknowledges an existing relationship between the staffer and his grandmother.

"Nana mentioned you have kept in contact with her. Thank you for that. She enjoys your friendship and care that you have for her," it reads. Ross goes on to offer her a job in his electorate office.

Ross has since told Newshub he didn't remember sending the text, that he was in psychiatric care around that time, and says the letter was simply a response to his grandmother's distress.

"No 80-year-old grandmother should have to feel like she's being used in some sort of political game," he said.

Parliamentary Services acts



The Parliamentary Service boss has written to the National Party staffer asking her to desist from attempting to contact Ross's grandmother or visiting their home.

Newshub.