Prime Minister Theresa May says revealing the figures might "uncover some uncomfortable truths." She says "too often ethnic minority employees feel they're hitting a brick wall when it comes to career progression."
Last year the government told companies with 250 or more employees to disclose the difference in median wages between men and women.
The government said Thursday that businesses including accountants KPMG, advertising firm Saatchi & Saatchi and the civil service had signed up to a Race at Work Charter, promising to recruit more ethnic-minority employees and help their careers advance.
The government will decide on mandatory reporting after a consultation.
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