Arun Reddy was detained late on Friday in connection with the edited footage, which falsely shows India’s powerful Interior Minister Amit Shah vowing in a campaign speech to end affirmative action policies for millions of poor and low-caste Indians.

Police in India said Saturday that they have arrested the social media chief of the country’s main opposition party over accusations that he misleadingly doctored widely shared video during an ongoing national election.

Arun Reddy of the Congress Party was detained late on Friday in connection with the edited footage, which falsely shows India’s powerful Interior Minister Amit Shah vowing in a campaign speech to end affirmative action policies for millions of poor and low-caste Indians.

Shah is often referred to as the second-most powerful man in India after Hindu-nationalist Prime Minister Narendra Modi, and the pair have been close political allies for decades.

Reddy “was arrested yesterday on investigation about... a doctored video of the Home Minister”, Delhi Police Deputy Commissioner Hemant Tiwari said, adding: “We produced him in the court, and he is in police custody.”

Authorities seized Reddy’s electronic devices for forensic verification, the Indian Express newspaper reported on Saturday, quoting an unnamed police officer who accused Reddy of having “cropped and edited” the video.

Congress spokesperson Shama Mohamed confirmed Reddy’s arrest but denied he was responsible for creating or publishing the clip. “He is not involved in any doctored video. We are supporting him,” she said.

Shah has been campaigning on behalf of Modi’s ruling Bharatiya Janata Party (BJP), which is widely expected to win a third term when India’s six-week election concludes next month.

Analysts have long expected Modi to triumph against an opposition alliance of Congress and more than two dozen parties that have yet to name a candidate for prime minister.

The Indian prime minister’s prospects have been further bolstered by several criminal investigations into his opponents and a tax investigation this year that froze Congress’s bank accounts.

Opposition figures and human rights organisations have accused Modi’s government of orchestrating the investigations to weaken rivals.

Modi’s government remains widely popular a decade after coming to power, largely due to its positioning of India’s majority Hindu faith at the centre of its politics despite the country’s officially secular Constitution, which in turn has left India’s 220 million-strong Muslim community feeling threatened by the rise of Hindu nationalism.

Since voting began in April, both Modi and Shah have stepped up campaign rhetoric on India’s principal religious divide in an effort to rally voters.

In the original campaign speech at the centre of the police investigation against Reddy, Shah vows to end affirmative action measures for Muslims established in the southern state of Telangana.

Modi used a campaign rally in April to refer to Muslims as “infiltrators” and “those who have more children”, prompting condemnation and an official complaint to election authorities by Congress.

But the prime minister has not been sanctioned for his remarks despite election rules prohibiting campaigning on “communal feelings” such as religion.