Shashi Tharoor has been bearing the brunt of attack since his tweet earlier this month.

Senior Congress leader Shashi Tharoor's letter of "explanation" to his party has taken his critics to task and suggested that the allegations against him of being a "Modi sympathiser" were just "based on hysterical reactions to distorted reporting of a single tweet".

In a strongly worded letter, Mr Tharoor reminded the state party chief Mullapally Ramachandran of his record in parliament and questioned if any of his critics could rival it.

"I intervened more than 50 times in parliament and spoke against 17 Bills with courage and conviction," he wrote. "Can any of my critics from Kerala say they have done so? Who on earth can credibly accuse me of a "volte face" from the stand I took when I sat alongside you in the last Lok Sabha?"

"Find me one leader from our state who has made 10% of the effort I made to study, research, anticipate and oppose the Modi Government on every Bill they sought to introduce against the spirit of our Constitution and the values of the Congress Party," his letter further said.

Mr Tharoor has been bearing the brunt of attack since his tweet earlier this month, which read: "As you know, I have argued for six years now that @narendramodi should be praised whenever he says or does the right thing, which would add credibility to our criticisms whenever he errs. I welcome others in Opposition coming around to a view for which I was excoriated at the time!"

It had created dismay in the Congress camp. While a number of leaders issued scathing criticism of Mr Tharoor, state party chief Mr Ramachandran had promised to demand an explanation and take action accordingly.

In his letter, Mr Tharoor reasoned that the voters across the country who switched support to the BJP would be more likely to be convinced by the Congress, if the party's views were balanced, instead of being permanently being skewed against Prime Minister Narendra Modi.

PM Modi, he said, has managed to rise the vote share of his party from 31% in 2014 to 37% in 2019.

The Congress, which managed only 19 per cent votes in both elections, should try to understand why, he wrote. For the voters who thought the BJP is delivering, the limitations need to be pointed out, he said.

"Yes, he built toilets, but 60% of them don't have running water; yes, he gave poor rural women gas cylinders, but 92% of them can't afford refills. But if we act as if he has done nothing, however flawed, and people still voted for him, then we are saying that people are stupid, which is not a position that wins you votes," his letter read.