The House of Lords has voted twice for legal protection to be given to the estimated 400,000 Dailts - so-called untouchables - who live in the UK.
MPs overturned the first Lords vote, but after peers again backed the plan on Monday, there has been a rethink.
Mr Cable said caste would in future be treated as "an aspect of race".
Keith Porteous Wood, of the National Secular Society, said: "We are delighted that the government has accepted that discrimination against caste should enjoy the same statutory protection as all other forms of protected characteristics.
"This is a victory for the Lords and their emphasis on protecting human rights."
Campaigners had said legislation was needed because thousands of people suffered abuse and prejudice because they were considered low caste.
They said existing laws offered no protection and said caste divided society unfairly, with those at the bottom expected to do dirty, poorly paid work while also being expected to - and forced to - look up to and respect higher castes.
Those arguing for action said such discrimination was outlawed in India and should be banned in Britain too.
In the House of Commons debate earlier this month the government acknowledged the existence of caste discrimination in Britain.
But equalities minister Jo Swinson told MPs: "This is an issue that is contained in the Hindu and Sikh communities. That's why we are working with those communities to address these problems."
She warned of concern that legislation could increase stigma rather than ease the problem and said that was why the government favoured tackling caste prejudice through an education programme instead.
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Were you aware of Caste discrimination going on in the UK?