Even with some representation in Parliament, the minorities complain they have been sidelined by the majority Buddhist Sinhalese. The Sinhalese-controlled legislature has done little to heal the wounds left from a quarter-century civil war that ended in 2009, and still refuses to acknowledge or investigate allegations of wartime atrocities by the government.
It has been accused of perpetuating rule by the country's 70 per cent Sinhalese majority instead of unifying the multicultural nation.
"We started 1947 as a united people, but over the past years we had an ethnic conflict ... to the point of a civil war," Prime Minister Ranil Wickremesinghe told a special session of Parliament on Tuesday to celebrate its 70th anniversary.
"We safeguarded democracy through all that, but we are yet to provide a political solution and unify the country," he said.
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Others say that, while democracy based on majority rule, has helped Sri Lanka on many fronts, it has also caused harm.
"In a country of ethnic divisions, majority rule can be a dictatorship by a permanent majority over a permanent minority," he said.
The divisions surfaced quickly after Sri Lanka, then known as Ceylon, won independence from British rule in 1948.
Within two years, the first post-independence Parliament stripped hundreds of thousands of mostly Tamil tea plantation workers of Indian origin of their citizenship and right to vote. That prompted fears among indigenous Tamil leaders, who demanded a federal form of self-rule in the country's north and east where they form a majority.
Non-violent campaigns by Tamil leaders demanding equal status for minority Tamils were attacked, and anti-Tamil riots killed hundreds of people. Thousands of other Tamils fled the country.