text: It says officers who file complaints are labelled as "troublemakers" and pressured to leave the force.
  A separate, unpublished police report has said disproportionate numbers of minority officers in some forces end up in the disciplinary system.
  The Association of Chief Police Officers says the data is "worrying".
  Speaking to Radio 4's  
            File on 4
   programme, President of the NBPA Charles Critchlow said:
  "I think the worst aspect is it appears that even senior officers are prepared to use instruments within the service, for example the disciplinary process, to put pressure on these officers and ultimately force them out of the organisation and that's something that we're very, very concerned about."
  He added: "I think there still exists within the police service a pattern of behaviour where officers, particularly junior officers, who make a complaint or challenge inappropriate behaviour - particularly if it's got anything to do with race - seem to be labelled as troublemakers."
  However, Mr Critchlow also stressed: "That is not to say that all officers are racist or discriminate against people, but there seems to be a problem in the police service when it comes to dealing with race issues."
  The BBC has also seen an internal draft report which shows police disciplinary procedures being used disproportionately against black and Asian officers in some forces.
  The report was compiled by academic researchers on behalf of Greater Manchester Police and includes data from the West Midlands Police and the British Transport Police.
  It acknowledges concerns from minority officers about unfair treatment and confirms that in the West Midlands, black and minority ethnic (BME) officers are almost twice as likely to be the subject of an investigation as white officers.
  Findings for the British Transport Police are broadly similar.
  The research also looks at officers being kept under surveillance in internal counter-corruption investigations and found that in Greater Manchester the proportion of minority officers being investigated is three times higher than that of white officers.
  Listen to the full report on File on 4 on BBC Radio 4 on Tuesday, 5 June at 20:00 BST and Sunday, 10 June at 17:00 BST
  Listen via the Radio 4 website
  Download the File on 4 podcast
  Got a story? Contact the File on 4 team
  In the West Midlands, the rate of allegations of corruption against BME officers is more than five times higher than the rate of allegations against white officers.
  The authors of the report are calling for further research and say their findings suggest the problems identified are not limited to the three forces featured in the research.
  Chief Constable of Bedfordshire Police Alfred Hitchcock, who is the Association of Chief Police Officers lead on equality, diversity and human rights, says he has not yet seen the internal report but says the data is "worrying".
  He told the BBC he would be speaking to other chief officers about the matter, but defended the way internal complaints are dealt with.
  "If there are matters relating to racist or improper behaviour, then those are investigated and people who are victims are treated as victims.
  "The service is very keen to make sure that we deal properly and appropriately with all staff and by doing that we would hope that people see us as being fair with all, and that is the objective," he said.
  File on 4's investigation also uncovered concerns about the slow progress forces have made in recruiting and promoting BME officers.
  Thirteen years after the Stephen Lawrence Inquiry recommended increased numbers of black and ethnic minority officers, the latest Home Office figures show more BME officers are leaving the police than joining.
  In 2010-11, 165 BME officers were recruited, but 204 left the service.
  Mr Hitchcock blames government cuts on police funding which has led to a recruitment freeze and subsequently a dip in numbers, but acknowledges the police leadership must do more:
  "If some people think that we've got this sorted I think they're living in a dream world. I think there is an awful lot of work for us still to do.
  "There is a danger that we put an over-negative spin on where we've come in the last decade because actually we've made fantastic progress. But that doesn't mean we stop; that means we actually need to renew and re-energise."
  Listen to the full report on File on 4 on BBC Radio 4 on Tuesday, 5 June at 20:00 BST and Sunday 10 June at 17:00 BST.
  Listen again via the Radio 4 website or download the File on 4 podcast.
target: Police forces are unfairly disciplining black and Asian officers who complain about racism, says the National Black Police Association.