Germany's leading right-wing party will press for Chancellor Angela Merkel to be "severely punished" for her immigration policies once it assumes a place in parliament, its leader said on Sunday.

The Alternative for Germany (AfD) party is projected to win up to 12 percent of the vote during Germany's federal election on September 24 and become the third-largest party in the Bundestag, polls show.

Alexander Gauland, cofounder of the AfD, told Reuters news agency the party would push for the creation of a new committee to examine Merkel's track record on refugees and migrants entering the country.

"We want Merkel's policy of bringing one million people into this country to be investigated, and we want her to be severely punished for that," he said.

"We're gradually becoming foreigners in our own country."

It was unclear what Gauland meant by "punishment".

Founded in April 2013, the AfD narrowly missed out on the five percent share of the vote required to win representation in parliament during the federal election in September of the same year.

The party, which advocates the closure of Germany's borders and the introduction of a minimum quota for deportations, could now become the biggest opposition force in the national assembly if the current coalition of Merkel's Christian Democratic Union party and the Social Democratic Party (SPD) is returned, as polling indicates is likely.

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That scenario would result in the AfD chairing the influential budget committee and allow its parliamentarians to open the general debate during budget consultations.

Georg Pazderski, a member of the AfD's executive board, told reporters his party would use its predicted role in the new parliament to highlight the cost of the refugee crisis and trouble in the eurozone.

"We'll have a voice when we're in parliament. We won't be an easy opposition," he said.

A number of candidates have already expressed their unwillingness to work with any new AfD parliamentarians, citing the group's controversial policy programme that includes the banning of the full Islamic face veil.

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Sahra Wagenknecht, a candidate for the Left Party, has pledged to vote against any AfD members who represent "Nazi views" being elected to positions of responsibility in the new parliament.

Wagenknecht, an MP since 2009, has declared elements of the AfD's far-right programme - such as the proposed ban on minarets - unconstitutional.

Right-wing parties have featured prominently in elections across Europe this year.

Marine Le Pen, leader of France's National Front party, won 34 percent of the vote in May's presidential election, and Geert Wilders, of the Dutch Party for Freedom, scored 13 percent in March, during the Netherlands' general election.