A long-serving midwife who said she was stopped from working because of her bright red hair has lost her appeal.
Donna Crichton, from Sleaford, lodged a grievance against United Lincolnshire Hospital Trust's (ULHT) uniform policy after being told in June her hair colour broke the rules.
She said she was "very disappointed" and would be "challenging" the trust's decision.
ULHT said it "cannot comment on individual confidential cases".
Ms Crichton said: "They're just unwilling to address their uniform policy is not fit for purpose, not in today's society."
"I feel extremely alienated and discriminated [against]."
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The Royal College of Midwives (RCM) said it had been "challenging the trust on this issue and on what appears to be an arbitrary decision to implement a policy that is in itself unclear and non-specific".
"Discussions are ongoing with the trust and unions, including the RCM, about the policy.
"This is because of concerns about the manner in which this policy has been written, disseminated and implemented, and its impact on the morale and motivation of midwives and other staff at the trust."
Ms Crichton said she first dyed her hair red in 2004 and it was not raised with her when she was taken on by the trust more than seven years ago.
She said she was only notified of the uniform breach and sent home at the end of June.
The action came months after the trust updated its uniform policy in October 2017.
ULHT previously said it expected staff to comply with its dress and appearance rules.