The US Department of Justice has accused Facebook of discriminating against American workers by giving hiring preferences to immigrants.
A lawsuit alleges the social media firm refused to recruit, consider or hire qualified and available Americans for more than 2,600 positions.
Those jobs instead went to foreigners on temporary visas, the lawsuit says.
Facebook disputed the allegations, but said it was co-operating with the department.
The lawsuit concerns Facebook’s use of temporary H-1B visas, which are often used by tech companies to bring highly skilled foreign workers to the US.
In its lawsuit, filed on Thursday, the department alleged that Facebook “intentionally created a hiring system” that favoured H-1B visa holders and other temporary workers over Americans.
The department said it filed the lawsuit after a two-year investigation into Facebook’s hiring practices.
The lawsuit seeks “back pay on behalf of US workers denied employment at Facebook” among other remedies.
“Our message to workers is clear: If companies deny employment opportunities by illegally preferring temporary visa holders, the Department of Justice will hold them accountable,” said Eric S Dreiband, the assistant attorney general for the department’s civil rights division.
“Our message to all employers – including those in the technology sector – is clear: You cannot illegally prefer to recruit, consider or hire temporary visa holders over US workers.”