It was a case that gripped India – the wife of a prominent politician found dead in a luxury hotel room, days after a series of messages emerged on Twitter appearing to suggest her husband had been having an affair.

Now, more than four years later, police in Delhi have charged Congress leader and ex-UN diplomat Shashi Tharoor with “abetment to suicide” over the death of his wife Sunanda Pushkar.

Ms Pushkar was found dead by her husband on the evening of 17 January 2014, with wide-ranging reports from the time including varying causes of death, from “poisoning” to a “deep bite” on her palm.

Investigators initially declared it a suicide, possibly due to an overdose of sleeping pills. But six months after the death, a forensic scientist alleged that he had been “pressurised” by political forces to amend the post mortem and act in an “unprofessional” manner. The cause of death has remained unclear.

Mr Tharoor, an MP for the main opposition Congress party, who also served as an under-secretary general at the UN for almost five years, becomes the first person charged in the case.

He strongly refuted the accusation on Monday afternoon, after Delhi Police released a charge sheet some 3,000 pages long that also accused him of subjecting his wife to cruelty. Party officials stood by Mr Tharoor and said the accusation appeared to be politically motivated.

“I have taken note of the filing of this preposterous charge sheet and intend to contest it vigorously. No one who knew Sunanda believes she would ever have committed suicide, let alone abetment on my part,” Mr Tharoor wrote on Twitter.

“If this is the conclusion arrived at after more than four years of investigation, it does not speak well of the methods or motivations of the Delhi Police.”

Rival BJP politicians have always led the charge in pointing the blame at Mr Tharoor for his wife’s death. In 2014, then-BJP leader Subramaniam Swamy went to court demanding a special investigation into the case.

But the circumstances surrounding Ms Pushkar’s death at the Leela Palace Hotel ensured it sparked the interest of the Indian public beyond political mudslinging.

Two days before she died, Ms Pushkar told two separate newspapers she had posted messages on her husband’s Twitter profile from the Pakistani journalist Mehr Tarar, alleging that the two were having an affair.

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One of the messages, apparently from Ms Tarar to Mr Tharoor, read: “I love you, Shashi Tharoor. And I go while in love with you, irrevocably, irreversibly, hamesha [forever]. Bleeding, but always your Mehr.”

The day after, the couple insisted they were happily married and that the “unseemly controversy” was the result of “some unauthorised tweets” from their accounts.

Taking again to Twitter on Monday, Mr Tharoor said police had recently told the High Court that they had not found “anything against anyone” in relation to Ms Pushkar’s death, and that it was “unbelievable” that they were bringing charges against him now.

Congress spokesperson Randeep Surjewala told the Press Trust of India the party rejected the charges against Mr Tharoor, alleging that he had been "hounded and persecuted" by the Delhi Police in collusion with BJP leaders.