FILE PHOTO: Belgrade mayor Sinisa Mali talks during an interview to Reuters in Belgrade March 24, 2015. REUTERS/Marko Djurica

BELGRADE (Reuters) - Serbia’s finance minister Sinisa Mali plagiarized parts of his Ph.D. thesis, the University of Belgrade said on Thursday, after his work was challenged by scholars prompting long-standing opposition demands for his resignation.

In a statement, the university, the largest and most prestigious in the country, said Mali, a trusted ally of President Aleksandar Vucic, “copied texts, or entire paragraphs, from the writings of other authors without mentioning their names, thus violating university’s ethical code”.

The university’s dean, Ivanka Popovic, said that its ethics board had unanimously decided to nullify the degree Mali had earned with his 2013 thesis on restructuring and privatization.

“The Board for Professional Ethics will deliver its final ruling to the Senate of the University for the ... annulment of (Mali’s) diploma,” she said.

Mali, who has repeatedly denied accusations over his diploma, said he would continue working.

“I am more focused on Serbia’s budget which is the job for which I am paid by Serbian citizens,” the state-run Tanjug news agency quoted him as saying.

The scandal over Mali’s thesis had prompted calls for his resignation from Serbia’s fragmented opposition and students who for almost a year have staged weekly protests against Vucic’s rule they see as corrupt and authoritarian.

Mali previously served as the mayor of the capital Belgrade.