An Asian officer has won a claim of victimisation against the Metropolitan Police, the BBC has learned.
Mr Virdi claims previous litigation against the Met blighted his career
Det Sgt Gurpal Virdi claimed his career had been blighted since being cleared of sending racist hate mail at a police station in west London.
Mr Virdi, 48, sued the force for racial discrimination and victimisation after failing to secure promotion in 2005.
Kingsway Employment Tribunal ruled he had been victimised but dismissed his race claim.
"The unanimous judgement of the tribunal is that [the Met] victimised the claimant," said the panel in its judgement.
Mr Virdi brought the case after he was turned down for promotion to detective inspector in 2005.
He claimed he was victimised because of previous litigation against the Met, which meant his application was treated "less favourably".
He won damages and an apology from the Met in 2002 after he was wrongly accused of sending racist mail to black and Asian officers at Hanwell police station and sacked.
However, the Met maintained Mr Virdi was turned down for the detective inspector job by an appeal panel because he did not have sufficient experience in leading investigations.
The tribunal ruled Mr Virdi had been "treated less favourably" than someone who did not have a history of litigation with the Met.
"There is no doubt in the tribunal's view that the appeal panel, at the very least subconsciously, was affected by their knowledge of the claimant and of the action he had taken."
Mr Virdi said his case was an example of the struggle ethnic minority police officers faced when trying to move up the career ladder.
"This should not be happening in a modern police service," he told the BBC News website.
"For all their public statements, the hierarchy seems to be paying lip service to the idea of an open and diverse police force."
Det Insp Mukhtiar Singh, chairman of the Met's Sikh Association, who gave evidence at the hearing, said Mr Virdi's case had "exposed some of the truths behind police promotion systems".
"Many black and ethnic minority officers continue to find it difficult to be posted within specialist posts and get promoted," he said.
"We do not want special treatment only equal opportunities.
Keith Jarrett, of the National Black Police Association (NBPA), said only 10 out of the country's 300 most senior police officers were from an ethnic minority.
"And in terms of representation in the other ranks it's pitiful," he said.
"It's still a massive problem for black staff to progress in the service."
He said the NBPA supported affirmative action as a means to improving diversity in police forces.
The Met Police said in a statement it would give "full and careful consideration to the written decision of the tribunal".
It welcomed the tribunal's decision to dismiss the race discrimination claim.
"However, the tribunal were critical of some parts of the appeal process and found that he had been treated less favourably...
"The [Met] is disappointed with this aspect of the finding and will be considering the judgement further.
"Mr Virdi remains a valued member of the [Met] and we will continue to provide him with the appropriate support to meet his professional development needs, as we do with all of our staff."
The tribunal will consider claims for compensation at a future hearing.