India’s opposition political alliance has vowed to conduct the first nationwide census of caste groups in nearly a century if elected, in a controversial attempt to galvanise marginalised voters it argues have been left behind by Narendra Modi’s Bharatiya Janata party.

Modi has dominated India’s politics for a decade in part by wooing voters across castes, presenting his party as a unifier of Hindus while stoking mistrust of India’s large Muslim minority.

But his rivals argue that this has obscured deepening hardship and joblessness among lower-caste Indians. The opposition, a loose alliance of parties known as INDIA, has promised to hold a socio-economic caste census and increase affirmative action and benefits for disadvantaged groups if elected in India’s six-week polls, which end on June 1.