Two unions are taking legal action against Uber, alleging that software used to verify drivers' identity is racially biased, and the firm has unfairly dismissed drivers.
Uber says it protects passengers by ensuring the right person is driving, and there is "robust human review".
Microsoft declined to comment on an ongoing legal case.
This week the Independent Workers' Union of Great Britain (IWGB) backed an employment tribunal claim for indirect racial discrimination on behalf of one of its members whose account, it says, was terminated following a facial verification error.
The IWGB is asking Uber to scrap the use of the technology.