NEW DELHI—India announced new rules on Thursday to regulate big social media firms, such as Facebook and Twitter, the latest effort by Prime Minister Narendra Modi’s government to tighten control over Big Tech firms. The rules come after Twitter ignored orders to drop content on farmers’ protests, fuelling the government’s zeal, dating from 2018, to clamp down on material it regards as disinformation or unlawful. The new measures will require big social media companies to set up a grievance redressal mechanism and appoint executives to coordinate with law enforcement, the government said in a news statement. The government said the guidelines in its code of digital media ethics were needed to hold social media and other companies accountable for misuse and abuse. Social media firms should be “more responsible and accountable,” Ravi Shankar Prasad, the minister for information technology, told reporters in outlining the rules. A detailed version of the …