P.K. Sinha, the principal adviser to Prime Minister Narendra Modi, has resigned, sources said on Tuesday.

Sinha, a retired IAS officer of 1977 batch, was appointed as principal adviser to the Prime Minister in September 2019, after a brief stint as an officer on special duty (OSD). Sinha was made OSD to the Prime Minister in August 2019, after he had served four years as cabinet secretary.

According to the order of his appointment, his tenure as principal adviser was co-terminus with the term of Prime Minister Modi or until further announcement, whichever was earlier. Sinha had also served as secretary in the power ministry.