Germany's Defence Minister has temporarily renounced his doctorate title following accusations of plagiarism.
German media allege that several passages of Karl-Theodor zu Guttenberg's 2006 thesis were lifted from other people's work, the BBC reports.
The minister has strongly denied the claims, while acknowledging that there were undoubtedly mistakes in the thesis and that he is unhappy about them.
Reports say Chancellor Angela Merkel had offered to support him if he explained his actions and apologised.
But her chief spokesperson made no comment on the minister's statement at a Berlin news conference, prompting journalists to walk out.
"I will temporarily, I repeat temporarily, give up my doctoral title," Mr zu Guttenberg told reporters in his statement minutes earlier. "My dissertation is not a work of plagiarism and I completely reject all such accusations."
List of allegations growing
The affair erupted when a law professor from Bremen University began writing a review of the thesis, with the aid of the internet.
Subsequent media reports alleged that one passage was copied word for word from a newspaper article; that another was taken from a public lecture, without attribution; and that a paragraph from the United States Embassy website was used without attribution.
The list of alleged instances of plagiarism has continued to grow as journalists and internet users pore over the thesis.
The University of Bayreuth, where Mr zu Guttenberg completed his PhD on constitutional developments in the US and EU, has given him a fortnight to respond to the allegations in writing.
Called to meeting with leader
Mr zu Guttenberg has come under intense pressure because of the claims, with one newspaper calling him "Baron Cut-and-Paste" and another "Zu Googleberg".
The charismatic 39-year-old minister with an aristocratic background, seen as a possible successor to Ms Merkel, had managed to avoid the public glare on Thursday because of an unannounced visit to northern Afghanistan.
But on his return he was called to a meeting with her to discuss the swirl of allegations.