The CDU is examining a party exclusion of the former head of the Office for the Protection of the Constitution, Hans-Georg Maassen.
Secretary General Mario Czaja had commissioned "the examination of party order measures up to and including party exclusion", said a CDU spokeswoman on Tuesday in Berlin on request.
The background is interview statements by Maassen on the subject of racism.
The deputy CDU federal chairman Karin Prien had previously called for Maaßen to be expelled from the party.
"If Mr. Maaßen is still a member of the CDU at our next federal executive board meeting on February 13, I will submit a request to the federal executive board to exclude him from our party," said Schleswig-Holstein's education minister on Tuesday in Kiel.
Maassen and his statements are no longer tolerable in the Union.
"His repeated use of anti-Semitic and conspiracy theory codes, his downplaying of racism and Nazi ideology and the openness he displays for right-wing extremists - all of this is incompatible with the values of the CDU," said Prien.
The CDU chairman Friedrich Merz sharply criticized Maassen's statements, but initially left open a procedure for a party exclusion.
"The statements made by Mr. Maaßen are again unacceptable," said Merz, who is also chairman of the Union faction in the Bundestag, on Tuesday before a meeting of the CDU/CSU deputies in Berlin.
Maassen had claimed in a tweet that the thrust of the "driving forces in the political and media space" was "eliminatory racism against whites".
Maassen had previously criticized German migration policy in an interview with journalist Alexander Wallasch for his blog.
He spoke of racism against "the native Germans", the existence of which was denied by "politicians and attitude journalists".
"This way of thinking is an expression of a green-red racial theory, according to which whites are regarded as an inferior race and that Arab and African men must therefore be brought into the country," said Maassen in the interview.