The Metropolitan Police discriminated against a black female officer because of her race and sex, an employment tribunal has concluded.
Britain's largest force faces a compensation claim from Carol Howard after a judgment found that she was "singled out and targeted" for almost a year.
The 35-year-old, a firearms officer in the Diplomatic Protection Group (DPG), brought a claim of discrimination at the Central London Employment Tribunal earlier this year.
A judgment issued by the panel which heard the case found that the Met "directly discriminated" against Ms Howard "on the grounds of sex and race" between 31 January and 29 October 2012.
A number of Ms Howard's complaints of "victimisation" were "well-founded", the tribunal added.
It concluded that her superior Acting Inspector Dave Kelly subjected her to "a course of conduct which was detrimental to her".
Lawyers for the claimant, from Purley in Surrey, will seek compensation from the Met for injury to feelings and aggravated damages. The size of her claim is being assessed.
Ms Howard' s lawyer Kiran Daurka, from Slater & Gordon, called for a public inquiry into how the force handles race discrimination claims.
She said: "This judgment is a damning indictment on the Met. "The conduct of the Metropolitan Police and some of its senior officers towards Carol Howard was deplorable over the last two years.
"My client was subjected to discriminatory treatment because she is black and because she is a woman.
"Fifteen years after the Met was branded 'institutionally racist' they have failed in addressing discrimination which pervades the system.
"This case shows that there needs to be a complete re-write of the Metropolitan Police's equality procedures and an independent investigation into existing measures purporting to deal with discrimination complaints. That's the only way to protect officers facing similar discrimination in the future."
Ms Howard was supported in her case by the Metropolitan Police Federation.
Its chairman John Tully said: " Whilst we are pleased that this judgment recognises that racist and sexist behaviour is unacceptable and is capable of being challenged, it is of concern that such issues are still prevalent in the Metropolitan Police Service, despite the many measures introduced to address the problem.
"Discrimination of any kind at any level is not acceptable in the police service and we must all work together to eradicate this."
A Scotland Yard spokesman said: "We are aware of the decision of the tribunal. We are disappointed at the tribunal's finding in favour of Pc Howard.
"The tribunal's decision will now to be given full and careful consideration. We will review the findings, take legal advice and take forward any learning or actions as appropriate."
The tribunal judgment said that within a few weeks of becoming her line manager Mr Kelly "formed the view...that the claimant was dishonest and not up to the standard required for DPG (Diplomatic Protection Group)".
He was said to have engaged on a course of conduct "that was designed to, and which in fact did, undermine, discredit and belittle" Ms Howard.
Her "every absence" was assumed not to genuine, she was booked on to shooting sessions, her commitment was challenged in front of colleagues and her application for an armoured response vehicle role was not supported, the panel found.
The tribunal heard that Ms Howard submitted a formal fairness at work complaint alleging that she had been subjected to unfair treatment by Mr Kelly in November 2012.
The following day he was said to have approached her and during the exchange he was "shouting at her and waving his hands", with the claimant leaving in tears.
Mr Kelly "acted in a hostile and aggressive manner" during the incident, the tribunal judgment said.
During the time covered by her claim, Ms Howard was one of just 12 female officers in the DPG and only one other was black.
The DPG provides protection for foreign embassies and missions in London.
The tribunal said in its conclusions: "DPG was at the relevant time, and probably still is, an almost exclusively male and predominantly white unit.
"The claimant stood out in the unit because she was different from almost everyone else in it because she was black and she was female."
She was the only black woman in the unit managed by Mr Kelly, the judgment said.
It went on: "She was singled out and targeted by him for almost a whole year. On his own admission he had formed a negative view of her from very early on.
"He doubted her honesty and her ability. He has not put forward any credible basis for forming such a view."
The tribunal was also critical of the way the force dealt with Ms Howard's fairness at work (FAW) complaint.
It said the process concluded that there was no evidence of race or sex discrimination "without having conducted a proper investigation into the matter".
The panel also found that a detective sergeant appointed to deal with the FAW complaint was asked to delete all references to discrimination and harassment relating to sex or race in a report.
This was done "not because they were not supported by evidence in the report, but because the claimant had brought a complaint of race and sex discrimination in the tribunal", the judgment concluded.
During the tribunal Ms Howard said she felt that she had been "singled out and chosen, as a black officer, to represent diversity and to change the public image of white police shooting black youth" after she was asked to take part in a newspaper photo shoot.
She also claimed the Met have not learned the lessons of the Macpherson report, the 1999 review into the investigation into the murder of black teenager Stephen Lawrence that branded the force "institutionally racist".