The Alternative for Germany (AfD), an emerging populist party founded three years ago, is backed by nearly one in six of the country's voters. Now a third of the party's MPs have been accused of anti-Semitism, calling the LGBT community a "degenerate" species, while AfD candidate Rudolf Muller was discovered selling Nazi memorabilia in his antique shop.

A Stern magazine undercover reporter went into Müller's shop and was sold money from concentration camps as well as medals with swastikas from World War II.

Selling such memorabilia is illegal in Germany. The AfD candidate pleaded ignorance, saying that many of his clients were French and American.

This rapidly rising party has won seats in 10 of Germany's 16 state parliaments.

Worryingly for liberals, the AfD gained 14% of the vote in the traditionally left-of-centre city of Berlin, grabbing support almost equally from Chancellor Angela Merkel's right-of-centre Christian Democrats and the centre-left Social Democrats (SPD).

The far-right party is on track to being the third largest party in the country, according to German public broadcaster ARD.

The latest opinion polls by ARD show that the AfD now has support from 16% of the country, but that has cast a spotlight on the extreme views of many in the party.

"Our growth has been breathtaking — any party would love to have so many new members and funding — but we must be careful not to let some lunatics into parliaments," said Ronald Gläser, freshly elected MP to the Berlin parliament, in a Sunday Times report.

Shortly after Kay Nerstheimer won a seat in the Berlin parliament, he relinquished the party whip after his membership to the German Defence League, a far-right extremist group under state surveillance for right-wing extremism and Islamophobia, came to light.

Nerstheimer has called gay people a "degenerate species" and characterised migrants as "parasites" and "sickening worms" on his Facebook page.

Berlin Mayor Michael Müller told Deutsche Welle that an AfD victory would be "seen throughout the world as a sign of the resurgence of the right and of Nazis in Germany."