Arvind Panagariya, an academic on leave from Columbia University, on Tuesday resigned as the NITI Aayog Vice Chairman, a sudden development that set off speculation about his successor.

Panagariya, appointed Vice Chairman of the restructured NITI Aayog in January 2015, disclosed that he has written to Prime Minister Narendra Modi, informing him that his leave was due to expire this month end and it was not possible to extend it beyond that period.

In his resignation letter, Panagariya has also said that he wants to resume his teaching job at Columbia University where he was working as a professor of Indian political economy.

The 64-year-old economist took over the post immediately after the erstwhile Planning Commission, a Nehruvian era institution was restructured and the new body was created.

Panagariya was the sherpa for the Prime Minister at the recently-concluded G20 meeting in Germany and he had always been a supporter of the Modi government, vocally backing its various reform measures, including the demonetisation.

There was no official comment by way of reaction but the development has come in the midst of speculation that there could be a reshuffle in the NITI Aayog where Bibek Debroy, who also is a staunch supporter of Modi and his economics, could be the likely successor.

Another name doing the rounds is that of Chief Economic Advisor Arvind Subramanian, who may be shifted to the NITI Aayog. There have also been murmurs of dissatisfaction in the top government circles about the performance of the NITI Aayog under the leadership of Panagariya, sources said.

Before NITI Aayog, Panagariya served as the chief economist of the Asian Development Bank and has also worked with the World Bank and the International Monetary Fund in various capacities.

In March 2012, he was honoured with Padma Bhushan, the third highest civilian award of the country.