Scotland Yard has refused to discuss allegations that a sleeper cell of al Qaida spies is being kept under secret service surveillance after infiltrating the Metropolitan Police.
According to the News of the World, in the past few weeks MI5 agents have identified four officers suspected of passing secrets from the force.
All four are allegedly Asians living in London and are feared to have links with Islamic extremists in Britain and worldwide terrorist organisations.
MI5 bosses reportedly fear the moles may have been planted to keep al Qaida informed of anti-terror raids, and may have already accessed sensitive information about ongoing operations.
Secret service agents are said to be monitoring the suspects, who work at different London police stations.
A Yard spokesman said: "All police officers and police staff, upon joining the Metropolitan Police Service and during their careers undergo a range of security checks.
"These are robust and vary accordingly to the type and sensitivity of the individual postings.
"We take matters of security very seriously and if any issues arise about individuals, they may be subject to further assessment.
"This could lead to restrictions being put in place relating to where an individual may work within the organisation or could lead to their dismissal."
