The Conservative Party claims Helensville people are disgusted with their electorate MP, John Key, for supporting the same-sex marriage bill.
Party leader Colin Craig has distributed 20,000 letters to residents there, urging them to not back the prime minister and same-sex marriage.
In the letter, a resident is quoted saying Mr Craig should stand for the electorate because Mr Key is 'too gay' to represent the area.
Mr Craig says the Prime Minister's decision not to listen to his electorate will cost him voters.
Mr Key says the Conservative Party leader is welcome to stand in his electorate of Helensville if he wants to. Mr Key says he is unfazed by any challenge from Colin Craig.
"I welcome any fair competition come election 2014, I wish him the best, but I have got the largest majority in the country so I hope I can continue to enjoy the support of the good people of Helensville in 2014".
Mr Key says the same-sex marriage bill has attracted only three calls to his electorate office.
Meanwhile, Helensville board member Brenda Steele, who has lived in the area all her life, finds the letter laughable and inaccurate.
She said Mr Key has strong support and his decision to support same-sex marriage, won't change a thing.