Permila Tirkey, 39, will receive compensation from Ajay and his wife Pooja Chandhok for making her work 18 hours a day for an hourly rate of 11 pence.
The employment tribunal in Cambridge ruled that the Chandhoks "wanted a servant in the Indian style".
"They wanted someone who would be not merely of service but servile, who would not be aware of United Kingdom employment rights and whom they could treat in the United Kingdom as (Pooja Chandhok's) father treated his servants in India," it concluded.
In addition to the compensation awarded by the tribunal, a further hearing to determine remedies for the discrimination and other matters will be held later this year.
Tirkey left their employment in 2013 by resigning "in circumstances which amounted to a dismissal", the ruling said.
Her lawyers said the case set a new legal landmark by establishing that workers in Britain who are treated poorly because they are from a lower Indian caste are protected by race discrimination laws.
"I want the public to know what happened to me as it must not happen to anyone else. The stress and anxiety that this sort of thing creates for a person can destroy them. I have not been able to smile because my life had been destroyed. Now I am able to smile again. Now I am free," Tirkey said after the judgment.
She was also barred from contacting her family in India and from bringing her Bible with her when the Chandhoks recruited her from Bihar in 2008.
Victoria Marks, her solicitor from the Anti Trafficking and Labour Exploitation Unit, said: "This is a very useful judgment for victims of modern day slavery. We hope that it will give other victims the courage to come forward and seek redress."
The tribunal ordered the Chandhoks to pay their former employee 183,773 pounds to make up the shortfall in what she should have received under the UK's national minimum wage.
Pooja, who hired Tirkey, was born in India to Afghan-Hindu parents and has been a British citizen since 2005.
Her husband was described as a Hindu born in Afghanistan whose parents sought refuge in Britain during the Afghanistan war in 1985 and has lived in Britain since 1999. He remains a German citizen.
Tirkey cared for the couple's twins, a boy and a girl, and performed other domestic duties such as cooking and cleaning, according to a 'Daily Telegraph' report.
The Chandhoks "concocted" a story about her working for them over an earlier period in order to circumvent UK immigration rules.
Pooja would call Tirkey "girl", despite being younger than her, which the tribunal accepted was "demeaning".
