The leader of Germany's main right-wing party is facing a backlash after comparing multicultural societies with migrants and refugees to a "compost heap".

Frauke Petry has caused political uproar since she became leader of the Alternative for Germany (AfD) party in July last year, for her anti-immigration and xenophobic rhetoric.

Earlier this year, the 41-year-old was condemned for insisting that the country’s border police should be authorised to shoot refugees trying to enter the country illegally.

Speaking in Stuttgart, Baden-Württemberg for German Unity Day on Monday, Ms Petry attacked calls for diversity from other German political parties, in comments which have been labelled by some local media as arguing for an ethically homogenous nation.

According to the Frankfurter Allgemeine Zeitung she said: “What are we to think of these ‘Germany is colourful campaigns?’ A compost heap is also colourful."

She also reportedly used the phrase "ragged proletariat of the Afro-Arab world" during her speech.

Her remarks have been lambasted as "repulsive" and "despicable" by fellow German political figures, The Local reports.

Refugees settle in Germany Show all 12 1 / 12 Refugees settle in Germany Refugees settle in Germany Germany Mohamed Zayat, a refugee from Syria, plays with his daughter Ranim, who is nearly 3, in the one room they and Mohamed's wife Laloosh call home at an asylum-seekers' shelter in Vossberg village on October 9, 2015 in Letschin, Germany. The Zayats arrived approximately two months ago after trekking through Turkey, Greece and the Balkans and are now waiting for local authorities to process their asylum application, after which they will be allowed to live independently and settle elsewhere in Germany. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity 2015 Getty Images Refugees settle in Germany Germany A refugee child Amnat Musayeva points to a star with her photo and name that decorates the door to her classroom as teacher Martina Fischer looks on at the local kindergarten Amnat and her siblings attend on October 9, 2015 in Letschin, Germany. The children live with their family at an asylum-seekers' shelter in nearby Vossberg village and are waiting for local authorities to process their asylum applications. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity Getty Images Refugees settle in Germany Germany Kurdish Syrian asylum-applicant Mohamed Ali Hussein (R), 19, and fellow applicant Autur, from Latvia, load benches onto a truckbed while performing community service, for which they receive a small allowance, in Wilhelmsaue village on October 9, 2015 near Letschin, Germany. Mohamed and Autur live at an asylum-applicants' shelter in nearby Vossberg village. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity Getty Images Refugees settle in Germany Germany Mohamed Ali Hussein ((L), 19, and his cousin Sinjar Hussein, 34, sweep leaves at a cemetery in Gieshof village, for which they receive a small allowance, near Letschin Getty Images Refugees settle in Germany Germany Mohamed Zayat, a refugee from Syria, looks among donated clothing in the basement of the asylum-seekers' shelter that is home to Mohamed, his wife Laloosh and their daughter Ranim as residents' laundry dries behind in Vossberg village on October 9, 2015 in Letschin, Germany. The Zayats arrived approximately two months ago after trekking through Turkey, Greece and the Balkans and are now waiting for local authorities to process their asylum application, after which they will be allowed to live independently and settle elsewhere in Germany Getty Images Refugees settle in Germany Germany Asya Sugaipova (L), Mohza Mukayeva and Khadra Zhukova prepare food in the communal kitchen at the asylum-seekers' shelter that is their home in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Efrah Abdullahi Ahmed looks down from the communal kitchen window at her daughter Sumaya, 10, who had just returned from school, at the asylum-seekers' shelter that is their home in Vossberg Getty Images Refugees settle in Germany Germany Asylum-applicants, including Syrians Mohamed Ali Hussein (C-R, in black jacket) and Fadi Almasalmeh (C), return from grocery shopping with other refugees to the asylum-applicants' shelter that is their home in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Mohamed Zayat (2nd from L), a refugee from Syria, smokes a cigarette after shopping for groceries with his daughter Ranim, who is nearly 3, and fellow-Syrian refugees Mohamed Ali Hussein (C) and Fadi Almasalmeh (L) at a local supermarket on October 9, 2015 in Letschin, Germany. All of them live at an asylum-seekers' shelter in nearby Vossberg village and are waiting for local authorities to process their asylum applications, after which they will be allowed to live independently and settle elsewhere in Germany 2015 Getty Images Refugees settle in Germany Germany Kurdish Syrian refugees Leila, 9, carries her sister Avin, 1, in the backyard at the asylum-seekers' shelter that is home to them and their family in Vossberg village in Letschin Getty Images Refugees settle in Germany Germany Somali refugees and husband and wife Said Ahmed Gure (R) and Ayaan Gure pose with their infant son Muzammili, who was born in Germany, in the room they share at an asylum-seekers' shelter in Vossberg village on October 9, 2015 in Letschin, Germany. Approximately 60 asylum-seekers, mostly from Syria, Chechnya and Somalia, live at the Vossberg shelter, which is run by the Arbeiter-Samariter Bund (ASB) charity, and are waiting for authorities to process their application for asylum 2015 Getty Images Refugees settle in Germany Germany German Chancellor Angela Merkel pauses for a selfie with a refugee after she visited the AWO Refugium Askanierring shelter for refugees in Berlin Getty Images

The interior minister of Badden-Wuttemberg Thomas Strobl told FAZ: “The strategy of these people is to make people scared. Therefore we should not even get involved with them.

“[The AfD] is not the saviour but the traitor of the Western world [...] they live for crisis and have no other goal but to expand this in everyday life.”

Andreas Stoch of the Social Democratic Party (SPD) of Germany said: “Once more the AfD has shown their hateful face. This blunder reaffirms that the AfD is by no means a bourgeois, but rather deeply inhuman.”

German trade unionist and SPD politician Leni Breymaier said: "Ms Petry's miserable hatred has at least reached the next level of language. People are systematically humiliated and played against each other. It is not the diversity that threatens social peace in Germany - it is the AfD".

Germany's AfD says Islam is not welcome

The AfD predicted in September it will become the country's third major party after next year's federal elections following gains they have made against Chancellor Angela Merkel's Christian Democrats (CDU).

Set up three years ago, the AfD has been buoyed by Europe's migrant crisis and the party's success has been attributed to its hard anti-immigration stance in contrast to Ms Merkel's refugee-friendly policy which has inspired widespread opposition.

The party has no MPs in the federal parliament in Berlin, but has members in more than half of Germany's 16 regional state assemblies.

An INSA poll this week showed support for the AfD down half a percentage point from last week at 15 percent but still up around 9 points from a year ago.