Scotland Yard has come under fire for deleting references to discrimination from internal reports to avoid problems at employment tribunals.
The practice was revealed as employment tribunal judges found that the force had discriminated against a black female officer because of her race and sex.
London Assembly member Jenny Jones called on mayor Boris Johnson to launch an investigation into whether other cases against the Met had been "contaminated in a similar way".
An internal Fairness at Work report on the case of Pc Carol Howard, 35, had references to discrimination removed over concerns it would be used in a tribunal, and two other cases were cited where similar material was deleted.
The employment judges said : " The tribunal is very concerned that the respondent's policy of not allowing Fairness at Work (FAW) advisers to make assessments of discrimination, and of instructing them to delete them when they do so, might mislead complainants and tribunals into believing that the FAW adviser has not found any discrimination when in fact he or she has done so."
In Pc Howard's case, the altered version of the report gave the impression that the FAW adviser Detective Sergeant Fiona Hepworth had not accepted the claims of sex and race discrimination, when in fact the opposite was true.
The draft report said: "I have read through all the material in this case and firmly believe that CH has been discriminated against by DK (then-Acting Inspector David Kelly) and not been given the time, support and space that she as a police officer is required. I feel that DK has harrassed her by constantly getting at her, treating her differently to her colleagues who are all male.
"In my opinion he feels threatened by her and keeps stating 'I am not frightened of her', this to me is making a deal of her race and that she is a female and if I was a colleague that DK was saying this to I would feel very uncomfortable and would need to challenge this."
Head of the FAW unit David Jones advised DS Hepworth to remove references to discrimination from the report, saying: "In making these changes I am mindful that Carol has a live ET (employment tribunal) and your report will be disclosable should the matter go to a full hearing."
During the tribunal, another two cases were cited where the practice was used. One concerned an allegation about whether or not an ageist remark had been made at a meeting.
Mr Jones said of a draft report on the case: " The use of the word discriminatory may cause problems if there are failings in this case which warrant the ET (employment tribunal) being settled."
In the second case, where the FAW advisor had written that an action could have been indirect discrimination, Mr Jones had said: " Any reference to discrimination can cause problems for the MPS at a later date if this case evolves into an ET. I suggest that you re-write this section."
The judges said: "The two incidents reinforce our view that the Respondent's guidance and policy about FAW advisors not making any findings of discrimination is related to the difficulties that that might cause to the MPS when defending allegations of discrimination in the employment tribunals."
Ms Jones said that the case would do "lasting damage" to Scotland Yard's reputation.
She said: "That the Met discriminated against an officer because of her gender and race is disgraceful. It is then made worse by the fact that an officer looking at her complaint deleted discrimination findings. There can be no place for racism or sexism in the police and I think this case will do lasting damage to the Met's reputation.
"If the Mayor is to restore trust in the Met then he must investigate if other complaints of discrimination have been contaminated in a similar way and if such instances are found then senior officers must be held to account."
Scotland Yard said that the force only considers discrimination as part of other processes, not Fairness at Work, due to "previous legal advice".
The force said in a statement: " It is essential that all staff have full confidence in our Fairness at Work (FAW) policy and we were already conducting a full review of the policy to ensure it meets everyone's needs. This case will help inform that review.
"Whilst it has never been part of the policy to delete discrimination allegations from FAW documentation we recognise that the practice of not considering them as a integral part of the process has caused concern and this will form a key part of the policy review.
"Where discrimination is alleged as part of a FAW complaint it is properly considered, but as part of other established processes such as the misconduct process, rather than within the FAW process.
"The MPS adopted this practice due to previous legal advice and not through any wish to hide or shy away from such issues."