Germany's embattled Education and Science Minister Annette Schavan has resigned over a plagiarism scandal, dealing an election-year blow to Angela Merkel's government.
A university panel on Tuesday found the Christian Democratic Union (CDU) minister guilty of "deliberate deception" for using foreign text passages without proper citation in her 33-year-old thesis.
Chancellor Merkel in a joint press conference with Schavan said on Saturday she had accepted her resignation "with a heavy heart" and praised the minister's achievements in her 17-year political career.
"She is putting the common good ahead of her personal interests," said Merkel of her long-time ally and personal friend.
Schavan, 57, reiterated she would challenge the university's decision legally, insisting that "I neither copied nor deceived" and saying that "the allegations have hurt me deeply".
Schavan's proposed successor is Johanna Wanka, 61, the former science minister of the states of Brandenburg and Lower Saxony. A trained mathematician, she is considered conservative and pragmatic.
Schavan became the second Merkel cabinet minister to quit over plagiarism, which also ended the political career of former defence minister Karl-Theodor zu Guttenberg in 2011.
At the time, Schavan, a tireless campaigner for excellence in education, was among the fiercest critics of zu Guttenberg, then a rising conservative star, saying he should be ashamed of himself.
The plagiarism case around Schavan and her own 1980 doctoral thesis, entitled "People and Conscience" first surfaced in April when an anonymous online posting accused her of cheating.
On Tuesday, after a lengthy academic investigation, a panel at Heinrich Heine University in Duesseldorf announced it was withdrawing her doctor title, a decision still subject to an appeals process.
The centre-left opposition Social Democratic Party (SPD) and other political parties quickly bayed for blood, demanding the resignation of the minister who was on a five-day visit in South Africa.
While many newspapers have argued Schavan should go, public opinion was mixed, a poll released on Saturday showed.
While 49 percent believed she should resign, 34 percent said she should stay, despite the scandal around her thesis, said the Forsa poll for news weekly Stern's online service.
Merkel will seek a third term in elections on September 22, hoping her CDU and its junior coalition partner, the pro-business Free Democratic Party (FDP), will stay in power.
Their challengers are the SPD, whose chancellor-candidate is former finance minister Peer Steinbrueck, and its preferred coalition partners the Greens.
Academic plagiarism scandals - fuelled by the advent of software that can easily find matching text passages in different digitised documents - have damaged several European officials recently.
Last year Hungarian President Pal Schmitt stepped down in a doctoral plagiarism scandal, while Romanian Prime Minister Victor Ponta resisted calls to resign over similar allegations.