The Metropolitan Police has revealed new allegations of racist abuse, bullying and violence involving at least 15 of its officers, threatening a return to the crisis that saw the force branded "institutionally racist" more than a decade ago.

The Met referred eight new cases to the police watchdog as part of a hasty review, which was ordered after a recording emerged of an officer calling a 21-year-old black man a "nigger" as he was being arrested after last summer's riots. Senior officers are scrambling to stamp out the crisis and prevent a repeat of the years of soul-searching that followed the Macpherson inquiry's damning report on the investigation of the murder of Stephen Lawrence in Eltham, south-east London, in 1993.

The revelations also raise questions about the role of the Independent Police Complaints Commission (IPCC), which is being asked to look again at cases it has already investigated. New allegations against police that came to light yesterday included:

* A racist attack against several youths in Hyde Park in 2011 which involved five police officers, all of whom remain on full duties;

* Mishandling of calls with a "racial element" by a PC in the force's central communication command in 2010;

* Claims that a group of officers in Newham, east London, used racist language. Three have been suspended.

* Racist bullying by police and civilian staff against community support officers over an 18-month period. Two police officers have been suspended;

"We're just glad that what we have seen for a long time has come out," Estelle du Boulay, the director of the Newham Monitoring Project, told The Independent last night. "It's a typical picture for us."

The 10 cases which have come to light in the past week include an alleged attack on a 15-year-old boy in the custody suite at an east London police station. Speaking outside Scotland Yard yesterday, the Met's deputy commissioner Craig Mackey, who led the review, said there could be more referrals to the IPCC in the future.

Six of the new cases involved officers blowing the whistle on colleagues, which Mr Mackey said showed the prevailing attitude in the force.

Details of the new allegations, which apparently date back to 2010, emerged two days after the head of the Metropolitan Police, Bernard Hogan-Howe, made an appeal to staff to report any racist colleagues.

"The commissioner made it clear after the first alleged incident came to light last weekend that we take the issue of racism extremely seriously," Mr Mackey said. "I want to reiterate – there is no room for racism in the Met."

Mr Mackey, who said the force had been working closely with the IPCC during the review, said the watchdog had agreed to look again at four cases, but was not able to say why.

In a statement, the IPCC contradicted the claims made by the Met. "We await receipt of the seven referrals from the [Metropolitan Police] and we will assess each case on its merits and make a decision regarding the level of IPCC involvement needed. At this stage, the IPCC has not agreed to investigate any of these latest referrals," it said.

The Macpherson Inquiry led to a huge change in British policing after its damning report into the failure of police to convict anyone for the murder of Stephen Lawrence in 1993. Two members of the racist white gang which stabbed the teenager to death were finally convicted earlier this year following a breakthrough in forensic science.