New Delhi: Chief economic adviser Arvind Subramanian dropped a bombshell on Wednesday by announcing his resignation after almost four years in a position that he described as "the best job he has ever had but not without controversies".

The sudden announcement was made public through a Facebook post by Arun Jaitley, currently minister without portfolio in the Modi government and recovering from kidney surgery.

It stirred questions about a palace intrigue, a bitter power struggle and deep disquiet within North Block ever since Piyush Goyal was pitchforked into the position of interim finance minister until Jaitley recovers.

Subramanian's term expires in May 2019.

At a news conference held later during the day, Subramanian said it still hadn't been decided from when his resignation becomes effective.

Jaitley said the chief economic adviser had informed him of his decision to step down a couple of days ago at a videoconferencing meet that he had held with bureaucrats in the finance ministry - an event that itself appeared to be shrouded in controversy.

Jaitley said in his post that Subramanian had told him "he would like to go back to the United States on account of pressing family commitments. His reasons were personal but extremely important for him. He left me with no option but to agree with him".

The "pressing family commitment" was the birth of Subramanian's grandchild. "I am expecting a grandchild in the US in September." But the excuse did not convince anyone.

There was no word from the Narendra Modi government on the acceptance of the resignation.

Maverick legislator Subramanian Swamy, who has attacked Jaitley and advisers like Subramanian in the past, jumped into the controversy by tweeting: "A wake up call for AS (Arvind Subramanian): Piyush holds Finance not Jaitley. So hand your quitting letter at the proper place or you may get charged for desertion from your post."

Subramanian was appointed as CEA at the finance ministry on October 16, 2014, for a period of three years. He had been persuaded by Jaitley to continue in office.

The outgoing chief economic adviser, who was on a sabbatical from his position as a senior fellow at the Peterson Institute for International Economics, is the third US-trained economist to leave the Indian government after attacks on them and their policies by Swamy, RSS affiliate Swadeshi Jagran Manch and a self-serving bunch of economists at the Niti Aayog.

Two years back, Subramanian had been publicly attacked by Swamy, who is believed to be close to the RSS, for being a green card holder and apparently supporting Washington's stand on intellectual property rights when he worked in the US in a manner harmful to Indian interests.

Jaitley, who was then the finance minister, had intervened to end the spat by clearly stating that the government supported the economist.

Earlier last month, the Swadeshi Jagran Manch had launched a blistering attack on the Modi government's decision to privatise Air India, a decision that Subramanian has strongly supported for years.

It isn't known whether the Modi government will immediately pick a successor to Subramanian.

The outgoing CEA told reporters a process to find one should start right away and that "the criteria should be competence, competence, competence". He felt that issues like loyalty shouldn't dictate the choice.

The right-wing brigade, of course, had a different view.

Ashwini Mahajan, national co-convener of the SJM, told The Telegraph: "We have requested Prime Minister Narendra Modi on Twitter to see that the next incumbent should be one who has faith in farmers, workers and entrepreneurs of Bharat and is not on a sabbatical from abroad."

As the general election draws near and the Modi government's sheen appears to be wearing off, officials say the Sangh parivar has started to flex its muscles and wants a say on all policy changes and key appointments.

Congress spokesperson Randeep Surjewala did not pass up the opportunity to attack the government.

"Financial experts' of Modi government are completely fed up by its colossal economic mismanagement, tepid economic reforms and financial anarchy," he said in a tweet.

During his press conference, Subramanian neatly side-stepped a loaded question on demonetisation - a policy that North Block insiders say that neither he nor his boss Jaitley ever whole-heartedly supported.

In an interview to the London-based Financial Times a year-and-a-half back, Subramanian had admitted he had learnt to watch his step on delicate topics that could upset the Modi government.

"I was asked for my views on the beef ban in Mumbai and said jokingly that if I speak on this I'll probably lose my job - and that went on the front page of The Indian Express," he told the Financial Times. "In that case, I was told to be a bit more careful."

Former RBI governor Raghuram Rajan has chosen to be very discreet in his comments about the Modi government since leaving office. One must wait to see whether Subramanian will be equally reticent.