Indian Prime Minister Narendra Modi has sparked off a decades-old row around Katchatheevu island, after he labelled the release of documents on the 1974 decision to hand the territory to Sri Lanka “eye opening and startling!”.

“New facts reveal how Congress callously gave away Katchatheevu,” tweeted the Indian Premier. “This has angered every Indian and reaffirmed in people’s minds- we can’t ever trust Congress!”

Eye opening and startling!

New facts reveal how Congress callously gave away #Katchatheevu.

This has angered every Indian and reaffirmed in people’s minds- we can’t ever trust Congress!

Weakening India’s unity, integrity and interests has been Congress’ way of working for…

— Narendra Modi (@narendramodi) March 31, 2024

He shared a link to an article from The Times of India, which detailed documents obtained through an RTI application by Tamil Nadu BJP chief K Annamalai. The documents quote Jawaharlal Nehru, India's prime minister at the time, as saying that he attached "no importance at all to [Katchatheevu]" and that he "would have no hesitation in giving up [India's] claims to it".

The island was ceded to Sri Lanka by Nehru's daughter and then prime minister Indira Gandhi, through an agreement signed by both governments in 1974.

During the armed independence struggle, as various movements sought a separate state of Tamil Eelam, relations between Tamil Nadu fishermen and their counterparts across the Palk Strait remained friendly. Both sides fished in the waters co-operatively, with fishermen from Tamil Nadu frequently assisting armed independence groups logistically.

As the Sri Lankan state began brutally supressing Tamil resistance movements, Indian fishermen who ventured south were beaten, arrested and even murdered. The issue of Katchatheevu has been politically contentious for decades with various parties in Tamil Nadu demanding the return of the island, to safeguard fishermen from continued Sri Lankan detention. There are still two cases pending in India’s Supreme Court, challenging the legality of the agreement with Sri Lanka.

Tamil Nadu fishermen continue to be regularly arrested by Sri Lankan forces in the meantime.

^{A group of Indian fishermen detained by the Sri Lankan navy last month.}

India’s foreign minister S Jaishankar added fuel to the issue at a press conference, when he read out excerpts of the documents and said that Congress “simply did not care", claiming they saw the island as a “little rock”.

Watch: Union Minister S. Jaishankar addresses a press conference explaining the relevance of the Katchatheevu issue today. pic.twitter.com/YQie0ivSzH

— IANS (@ians_india) April 1, 2024

He went on to detail how ceding the island led to the arrests of Tamil Nadu fishermen by Sri Lanka, stating “in the last 20 years, 6,184 Indian fishermen have been detained by Sri Lanka”.

“And in the same period, 1,175 fishing vessels – Indian fishing vessels – have been seized, detained, apprehended by the Sri Lankans.”

"We are talking about 1958 and 1960... The main people in the case wanted to make sure that at least we should get the fishing rights... The island was given away in 1974 and the fishing rights were given away in 1976... One, the most basic recurring (aspect) is the indifference shown by the then central government and the PMs about the territory of India…That fact is they simply did not care."

Meanwhile Annamalai demanded that both Congress and the Dravida Munnetra Kazhagam (DMK) - Tamil Nadu’s ruling party that was also in power at the time – apologise for their role in the decision. Speaking to journalists Annamalai said,

“When the Congress government at the Centre handed over the island to Lanka, DMK also had a role in this process. It seems the current Tamil Nadu CM has written 21 times to EAM Jaishankar demanding retrieval of the island. But the fact is that had the same DMK and the then CM Karunanidhi opposed the move 45 years ago, the Centre wouldn’t have handed it over to Sri Lanka.”

"The DMK had written several letters to the foreign ministry over the past many decades, upholding the rights of Tamil Nadu's fisher people over Katchatheevu. The BJP woke up to the issue only now, just as elections are nearing," DMK spokesperson Saravanan Annadurai told the BBC.

Whilst words continue to be traded by parties across India, former Foreign Secretary and High Commissioner to Sri Lanka Nirupama Menon-Rao warned the impact on bilateral ties “cannot be inconsequential”.

So far, Sri Lankan state has been firm in its response.

 "As far as Sri Lanka is concerned, Katchatheevu island falls within the Sri Lankan line of control,” minister Jeevan Thondaman told the Indian Express. “So far, there has not been an official communication from India to return the powers of Katchatheevu island… If there is such a communication, the foreign ministry will reply to that."

The issue has been raised ahead of the Indian general election in Tamil Nadu, which is due to be held on 19 April. The Bharatiya Janata Party (BJP) has been working at making inroads in the state, where it won none of the state's 39 seats in India's 545-member parliament during the last election.