When President Obama visits India next month, it is quite certain that he will pay tribute to Mahatma Gandhi, perceived around the world as one of history's most celebrated symbols of liberation, and a source of inspiration for the US president himself.

But there are calls within India for Obama to look further than Gandhi in paying homage to Indian heroes. For India's community of 167 million Dalits, once known as "untouchables", the true icon is Dr B R Ambedkar. Himself an untouchable, Dr Ambedkar gained doctorates from Columbia University, where President Obama, too, was educated, and at the London School of Economics, before becoming the architect of independent India's new constitution.

Relatively little-known internationally, Ambedkar has accrued almost divine status as a focal point for Dalit aspirations. Within India, Ambedkar appears everywhere. His statues easily outnumber those of Gandhi. Deep in communities of Dalits, you will hear the greeting, "Jai Bhim", meaning "hail Bhimrao [Ambedkar]". You will see his portrait in any self-assertive Dalit's home, and his name is spoken with pride. When, in 2006, the nation marked the 50th anniversary of his death, over 800,000 Dalits crowded to pay him their respects in Mumbai.

Dalits stress that, unlike the Mahatma, Ambedkar challenged the very existence of the caste system as the basis for discrimination against Dalits. It is because of Ambedkar, they say, that Dalits play any role in India's political and administrative structures – albeit a limited part. That is why anti-caste activists are urging Obama to pay homage to Ambedkar as a true giant of the cause of liberation from oppression.

These calls are just one sign of the increasingly powerful vocalisation of Dalit aspirations for recognition of their cause, and for social, economic and cultural equality. Dalit hopes for liberation from caste oppression – and it is important to add that Dalits suffer discrimination in every religious community – are resonating increasingly loudly around the world. The issue has gained profile at the United Nations, the UN Committee for the Elimination of Racial Discrimination having charged the Indian government to bring about clear improvements in a number of areas. NGOs continue to press companies investing in India to tailor their corporate social responsibility policies to address the specific challenges of caste discrimination.

Two campaigners against caste discrimination, S Anand and Meena Kandasamy, visited London last week to highlight the cause by speaking at events around a photography exhibition, "Being Untouchable".

The exhibition, by Marcus Perkins for CSW, offered a sympathetic series of portraits of the many different faces of untouchability in modern India, in a powerful reminder of the plight of the tens of millions of victims among the Dalits: the woman who cleans excrement from a dry latrine because it is her caste job; the young girl pushed into burning ashes because she walked on a path reserved for "high" castes who may never get justice; the destitute who may always be excluded from education and opportunities. Theirs are the stories that truly need to be heard amid the cacophony of coverage of India's economic boom.

Reading from her deeply moving 2006 poetry collection at the launch last week, Meena Kandasamy offered a poignant reminder of the depth of Dalit aspirations for drastic change:

We will rebuild worlds from shattered glass and
remnants of holocausts.
[. . .] It will begin the way thunder rises in our throats and we
will brandish our slogans with a stormy stress and
succeed to chronicle to convey the last stories
of our lost and scattered lives.

David Griffiths is south Asia team leader at Christian Solidarity Worldwide.