Microsoft is facing its second round of lawsuits this year alleging that it has engaged in racial discrimination against black people within the organisation.

One of the two suits filed last week in the US District Court in Seattle is being dealt with by attorney Johnnie Cochran, who is best known for having defended OJ Simpson during his murder trial.

Cochran, Cherry, Givens & Smith is representing Landruff Trent, who claims that the software giant acted in a discriminatory fashion when evaluating and promoting black people.

The law firm also plans to work with the Seattle offices of Cohen, Milstein, Hausfield & Toll, which filed a class action lawsuit last October on behalf of Monique Donaldson. The former Microsoft staff member alleged she was the victim of racial and gender-based discrimination and the two cases will be heard together.

The second suit was filed in the federal court by attorney Carl Taylor Lopez on behalf of former Microsoft employee, Ronald Douglas. Douglas argues that he was paid less and given fewer stock options than white personnel in similar positions.

A Microsoft spokeswoman said: "Microsoft takes this issue very seriously. We're doing a lot of work in this area to promote ethic minorities, both within Microsoft and from a community and charity point of view. We are already involved in a couple of suits and we're trying to address these issues."

Last month, Microsoft was hit with a $5bn class action suit from seven current and former staff for alleged racial bias.

The suit, which was filed in the US District Court in Washington, claimed that Microsoft violated civil rights and discriminated against black employees in evaluations, compensation, promotion, wrongful termination and retaliation.