Sikh detective Gurpal Virdi from Cranford has lost his appeal against a decision to clear Met Police bosses of victimisation.
Gurpal Virdi was awarded £70,000 after winning an employment tribunal in June last year, only for judges to overturn the ruling on appeal.
The Court of Appeal upheld the decision on Tuesday after it was challenged by the 50-year-old.
A spokesman for the Met said it was pleased by the verdict but 'disappointed he felt it necessary to bring this case at all'.
"Our policy and practice is designed to allow all members of the service to fulfil their potential regardless of ethnicity or faith," he added. "DS Virdi is and remains a valued officer of the MPS."
The Met was ordered to pay DS Virdi £240,000 In August 2000, after wrongly accusing him of sending racist hate mail to himself and fellow black and Asian officers at Hanwell Police Station.
He claimed resentment over that decision led to him missing out on promotion five years later, and tribunal judges awarded him another £70,000 in damages last June.
But the Met successfully appealed that verdict, insisting the job had gone to a better-qualified candidate.
DS Virdi, who missed out again on promotion to inspector last year, has three further employment tribunal cases pending against his employers.
Met chiefs have admitted destroying potentially harmful evidence relating to his latest case.
However, they claim notes taken by the detective's promotion panel were 'shredded in error'.
DS Virdi last month described himself as the 'Colin Stagg of the Met', referring to the man wrongly accused of killing model Rachel Nickell on Wimbledon Common.
"Everyone knows I'm innocent and the Met are not accepting it," he said.
A high-profile inquiry into discrimination in the Met, focusing on employment and career progression among officers from ethnic minorities, began on Wednesday.
The Metropolitan Police Authority Race and Faith review was launched by London Mayor Boris Johnson following a string of claims by officers, including former Hounslow borough commander Ali Dizaei.