The Metropolitan Police (Met) has been accused of "foul play" after reneging on an agreement not to appeal a tribunal ruling, the BBC has learned.
Gurpal Virdi claims the Met is paying lip service to "learning the lessons"
The force lost a victimisation case brought by Det Sgt Gurpal Virdi after he failed to secure promotion in 2005.
The Met said it would not appeal the decision if Mr Virdi agreed not to appeal a race claim, which was thrown out at Kingsway Employment Tribunal.
"This undermines trust in the force," said the Black Police Association.
A letter dated 30 October from the Met's legal team to Mr Virdi's solicitors stated it would forgo an appeal in the "interests of moving forward".
"My client considers that there is a good ground of appeal in relation to the victimisation finding," said the letter signed by Andrea Cunningham and obtained by the BBC News Website.
"However, I am instructed that in the interests of moving forward, if DS Virdi agrees not to exercise his right of appeal my client would also be willing not to pursue an appeal."
However, the Met lodged an appeal on 19 November, the last day of the appeal window, even though Mr Virdi's solicitors had not appealed.
Mr Virdi said the Met's "oft bandied line" about "learning the lessons" was an empty statement.
"This is how the Met plays dirty by saying one thing then doing the opposite at the tax payer's expense," he said.
"The appeal is now going to be costly and add more delays to any form of settlement.
"Many ethnic minority officers lose employment tribunals because the Met plays games when it loses."
The Met confirmed it has appealed against the employment tribunal decision, issued on 10 October.
"Having taken independent legal advice and as a public body, we have a duty to consider an appeal where Senior Counsel strongly indicate that there are clear grounds for doing so," it said in a statement.
Alfred John, chairman of the Met's Black Police Association, said the force's actions amounted to "foul play".
"Gentlemen's agreements such as this are extremely important to the legal process by helping to save taxpayers' money," he said.
"But when the Met moves the goal posts, bearing in mind the accountability of the organisation has been more than brought into question recently, this is in no way acceptable.
"The Met's actions will only serve to undermine trust within the organisation.
"If the Met can't gain the trust of its own employees what chance has it got of winning the trust of Londoners?"
Mr Virdi, 48, 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.