Human Rights Watch (HRW) said failure of Indian governments since 1984 to prosecute those involved in the "organised carnage" shows the need for police reforms and communal violence law.
The observation by HRW comes as India will on Friday commemorate the 30th death anniversary of former Prime Minister Indira Gandhi, whose assassination by her Sikh bodyguards triggered the riots against the community in 1984.
"India's failure to prosecute those most responsible for the anti-Sikh violence in 1984 has not only denied justice to Sikhs, but has made all Indians more vulnerable to communal violence," South Asia director of Human Rights Watch Meenakshi Ganguly said in a statement.
"The authorities repeatedly blocked investigations to protect the perpetrators of atrocities against Sikhs, deepening public distrust in India's justice system," she said.
"The new Indian government should seek police reforms and enact a law against communal violence that would hold public officials accountable for complicity and dereliction of duty," the HRW said.
The rights group said Indian authorities should implement police reforms to insulate the police from political pressure to protect perpetrators, which occurred after communal violence in 1984 in Delhi, 1992 in Mumbai, 2002 in Gujarat and 2013 in Muzaffarnagar.