Metropolitan Police officers fear they will be accused of racism when dealing with complaints against ethnic minority colleagues, a draft report suggests.
Black and Asian officers are twice as likely to be investigated
It found white officers tended to refer complaints upwards rather than use their initiative to resolve the matter.
And the Met's report, obtained by BBC Radio 4's Today programme, said black and Asian officers felt some specialist sections remained closed to them.
But it said progress had been made since the Stephen Lawrence inquiry.
The inquiry into how the black teenager's murder in Eltham, south east London, was investigated found the force was "institutionally racist".
'People are fearful'
A report by the Met's Assistant Commissioner Tarique Ghaffur found Black and Asian officers are twice as likely to be investigated or receive formal written warnings as other officers.
He told the Today programme: "That is a worrying aspect.
"Because people are fearful, legal procedures take over and things get formalised when they could be sorted out at source."
Tarique Ghaffur says training and discipline remain a challenge
"Post Lawrence we made huge inroads in the way we deliver services to Londoners.
"Internally, the way we recruit, the training, the way we deal with discipline and having sufficient role models remains a challenge for us."
Chairman of the Commission for Racial Equality Trevor Phillips said the essential question was 'Can the police do better at tackling crime?'
He said: "The fact is we need more cops. With this kind of behaviour going on you won't attract young people, either white or black.
"The police need wide public support to tackle crime and this kind of thing erodes public confidence.
"Nothing is changing very much which is why we will need to take some pretty radical steps.
Trevor Phillips says radical steps must be taken
"Managers should get on and do their job and they should have nothing to fear if they are being fair."
News of the draft report comes less than a month after the force's commissioner, Sir John Stevens, said officers were "nervous" about dealing with race issues.
He was speaking as he opened the Morris Inquiry - set up after criticism over a number of cases involving ethnic minority officers.
They included the cases of Superintendent Ali Dizaei, who was cleared of allegations of dishonesty at the Old Bailey last September and of Sikh officer Sergeant Gurpal Virdi, who was sacked after being falsely accused of sending hate mail.
Assistant Commissioner Ghaffur's findings will form part of the Met's submission to the Morris inquiry.
Former union leader Sir Bill Morris is expected to release his findings in the summer.