The worker has alleged he was made to work without pay in "slavery-like conditions" by Monirul Islam and his wife Fahima Tahsina Prova, and was threatened and abused.
The anti-trafficking unit of NGO Safe Horizon - that represented Khobragade's domestic help Sangeeta Richard - filed a civil complaint last Friday in Manhattan federal court on behalf of Mashud Parves Rana.
The complaint states that Islam and Prova "trafficked" Rana into forced labour and involuntary servitude.
The lawsuit comes just months after Khobragade was arrested on charges of visa fraud and making false statements about the visa application of Richard, a domestic help she had got from India.
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Prosecutors had alleged Richard was "grossly underpaid and overworked" and Khobragade paid her as little as USD 1-3 an hour instead of the USD 9.75 rate agreed to.
Rana, who worked for the diplomat from September 2012 until earlier this month, is seeking unspecified money damages.
Islam dismissed as baseless Rana's allegation.
He told bdnews.Com that Rana sued him and his wife in a bid to gain permanent residency in the US.