SINGAPORE (Reuters) - The founding dean of a prominent Singapore school said on Monday he was stepping down, four months after he stirred a heated debate in the city-state with the comment that small countries like Singapore must “always behave like small states”.

Kishore Mahbubani, a long-time diplomat and the wealthy city-state’s former envoy to the United Nations, said he had written to the board of the Lee Kuan Yew School of Public Policy saying he would step down as dean at the end of the year.

The announcement followed a high-profile expulsion by the government of a professor at the school, a China-born U.S. citizen, who was accused of being an agent of influence for a foreign country.

In the statement to the school’s governing board, Mahbubani cited a double heart bypass operation last year and said he wanted to “focus on a new career that involves more time spent on reading, reflection and writing”.

“I realize that the time had come for me to take a fresh look at what I should achieve over the next decade as I enter my 70s,” he said. Kishore is 69 and has served 13 years as dean.

Kishore’s statement did not refer to the controversy fueled by his column in July that Qatar’s experience of conflict with its Arab neighbors offered big lessons for small countries.

In the piece titled “Qatar: Big lessons from a small country”, Kishore warned that Singapore could face the fate of the Gulf state which believed it could act as a middle power and exercise influence beyond its borders “because it sits on mounds of money”.

“I would like to emphasize as strongly as I can that this Qatar episode holds many lessons for Singapore,” he wrote in Singapore’s Straits Times newspaper. The first lesson, he said, was: “Small states must always behave like small states.”

Public criticism or perceived admonishments of the government are rare in Singapore, one of the richest and most politically stable countries in the world.

His comments drew a sharp rebuke from Singapore’s political leaders and fellow former foreign service officials as flawed and intellectually questionable. A veteran diplomat, Bilahari Kausikan, called them “muddled, mendacious and indeed dangerous”.

Mahbubani could not be reached for comment.

A spokeswoman for the National University of Singapore, where the Lee Kuan Yew school is an autonomous postgraduate school, said: “Professor Kishore Mahbubani’s decision to retire is unrelated to the article mentioned.”

The school is named after modern Singapore’s founding father.