Large parts of Karl-Theodor zu Guttenberg's 2006 legal dissertations were found by BayreuthUniversity to have been copied and he stood down before it issued its damning verdict in May 2011.
The University of Bayreuth, where he completed his PhD on constitutional developments in the US and EU, has given him a fortnight to respond to the allegations in writing.
Mr Guttenberg, a member of the Christian Social Union (CSU) - the Bavarian sister party of Mrs Merkel's conservative Christian Democrats (CDU) - was also stripped of his PhD by the University of Bayreuth last year after evidence of his plagiarism emerged.