BERLIN - German Education Minister Annette Schavan announced her resignation on Saturday after a university stripped her of her doctorate for plagiarism.

Schavan is a close ally of German Chancellor Angela Merkel. The move is said to be a blow to Merkel as she is trying to win a third term in office.

Merkel said she had accepted the resignation "with a heavy heart" after Schavan's former university stripped her of her doctorate over plagiarism when writing her thesis "Person and Conscience" 33 years ago, media reports said.

A faculty committee of Duesseldorf's Heinrich Heine University voted last Tuesday to deprive Schavan of her doctorate after the committee found that parts of her dissertation had plagiarized "systematically and intentionally."

Schavan insisted she would still fight the university's ruling.

Merkel, speaking alongside with Schavan before reporters, said the minister offered to quit Friday evening and she accepted.

Johanna Wanka, incumbent Minister of Science and Culture of the German state of Lower Saxony, will take over as the education minister.

Schavan is the second German cabinet minister to lose a doctorate because of plagiarism. Karl-Theodor zu Guttenberg resigned as Defence Minister in 2011 after it was found that he copied large parts of his dissertation.

Observers had said that an early resignation of Schavan, though still an embarrassment for Merkel, would reduce the potential damage to Merkel's campaign to win reelection in the general elections which is set for September 22 this year.