Allegations of "serious corruption and malpractice" within the Met Police are being investigated by the Independent Office for Police Conduct (IOPC).
IOPC director Jonathan Green said claims of racial discrimination within the Met were also being investigated.
The Met said it was "fully co-operating" with the investigation.
A source told the BBC the investigation was at an early stage and may involve up to 14 officers.
It is claimed there are officers in the Met's Directorate of Professional Standards (DPS) who are said to have interfered with or curtailed investigations, according to Mr Green.
He added: "The investigation includes alleged interference in, and curtailment of, investigations by potentially conflicted senior officers, failure to investigate allegations of wrongdoing, systemic removal of the restrictions of officers under investigation and racial discrimination.
"As part of this investigation, three officers have been served with gross misconduct notices and one of those officers is also under criminal investigation.
"Assessments on the status of a number of other officers remains ongoing."
According to The Sunday Times, three whistleblowers from the Met approached the IOPC to allege members of the DPS were shielding officers from a range of allegations.
A Met spokesman said: "The Metropolitan Police Service has referred allegations regarding the conduct of a number of MPS personnel to the IOPC which is conducting an independent investigation.
"The MPS is fully co-operating with the IOPC investigation."
Over the last 50 years the Met has been through a series of corruption scandals.
BBC News.