As the election campaign in New Zealand sweeps across the country, Prime Minister John Key's election posters were marred by anti-Semitism messages. Although Mr Key is not a practicing Jew, he is the son of a Jewish woman who sought refuge from Europe.

According to local media, several billboards of the prime minister were defaced. Some had messages scrawled like, "Lying Jew c***sucker." The image of Mr Key was also altered to make him appear on the billboard with a black hat and sidelocks.

Mr Key, the National Party leader, is actively campaigning for a third term in office. He told reporters that he was "disappointed" for the Jewish community. He acknowledged his Jewish roots but he said his past was already well-known to the people. Mr Key added that some of his maternal relatives were brought to concentration camps.

The prime minister appealed to his detractors that the members of the Jewish community in New Zealand are decent and hardworking. He said the Jews in the country don't have to be dragged into the political campaign against him.

New Zealand Jewish Council President Stephen Goodman said the Jewish community was concerned about the rise of anti-Semitism in recent times. He denounced the defamation of Mr Key's election campaign billboards and said it was "unacceptable."

Goodman said New Zealanders should be free from "abhorrent discrimination." He called on authorities to deal with those who vandalised Mr Key's billboards as soon as possible.

The vandalism occurred after news of Labour Party candidate Steve Gibson broke for posting a message on social media and calling Mr Key a "Shonky Jonkey Shylock... nasty little creep with a nasty evil and vindictive sneer." The Facebook post has since been deleted. He was censured by Labour party leader David Cunliffe. Gibson had apologised on Facebook for his offensive post.

Reports said Mr Key is preparing for a "tough" election on Sept 20 as Nicky Hager's book, Dirty Politics, had added controversy. The prime minister has been accused of "playing dirty" in politics. In a poll conducted by One News Colmar Brunton, the National Party was down to 50 per cent in approval ratings. New Zealanders who preferred Mr Key as the prime minister had declined to 45 per cent. The poll was taken before the book came out and accused senior officials of working with right-wing bloggers to attack rivals in politics.