Addressing Mrs Merkel with the words "Dear Angela,", Ms Schavan thanked the chancellor for her friendship.
"I think today is the right day to leave my ministerial post and to concentrate on my duties as a member of parliament," the 57-year-old said.
"I will not accept the university's decision and will take legal action. I have never copied nor plagiarised. The accusations hit me very hard."
Ms Schavan added that her main priority was to protect her department and the government.
"First the nation, then the party, then myself," Ms Sc
