German Chancellor Olaf Scholz has condemned an alleged far-right meeting at which plans to deport millions of people were discussed.
German media said politicians from the far-right AfD and neo-Nazis met at a villa near a lake outside Berlin.
The deportation of people with a non-German ethnic background, including citizens, was allegedly discussed.
Mr Scholz said no-one should be discriminated against because of their origins in Germany.
The Correctiv investigative outlet reported that last November around 20 people attended the secret meeting near Potsdam, outside Berlin.
Correctiv said that these included senior figures from the far-right Alternative for Germany (AfD), including Roland Hartwig, a close associate of party leader Alice Weidel.
Neo-Nazis from across Germany and Austria, as well as a member of the white supremacist Generation Identity group attended, the outlet said.
Two members of the centre-right Christian Democrats (CDU) party are also said to have participated.
Much discussion allegedly focused on so-called "remigration" - the removal of people with non-German ethnic backgrounds, even if they are citizens of Germany.
Correctiv reported that there were no objections over the plan in principle, only doubts over its feasibility.
Officially, the AfD rejects the principle of remigration. But Gerrit Huy, an AfD member of the German Parliament, said she had believed in the idea for years.
This was why, she said, the AfD no longer opposed dual citizenship: because it would allow migrants to be stripped of their German citizenship more easily, as they would have another to fall back on.
Responding to the report, Mrs Huy contradicted the party's official stance by saying the AfD "is committed to remigration".
The party confirmed to the AFP news agency that Mr Hartwig had attended the conference, but denied it would change its policy on migration.
Chancellor Scholz said in a statement on X (formerly Twitter): "We will not allow anyone to differentiate the 'we' in our country based on whether or not someone has an immigrant background."
He added that participants could be investigated by the Office for the Protection of the Constitution, the domestic intelligence agency.
"Learning from history is not just lip service."
Last year, a recently-elected AfD member of the Bavarian Parliament was detained by police over alleged Nazi salutes.
The far-right party is currently polling second in Germany, behind the CDU.