A Muslim police officer is taking legal action against the Metropolitan force following his removal from a top protection squad.
Important dignitaries are protected by armed police officers
Amjad Farooq, 39, was a member of Diplomatic Protection Group SO16, which guards dignitaries such as Tony Blair.
PC Farooq had been working for the DPG for six weeks when he was told he had failed his security checks.
His solicitor, Lawrence Davies, told the Independent: "Muslims are labelled guilty by association."
The newspaper also says PC Farooq denies any links to extremist groups or inappropriate behaviour.
It claims he was told he was a threat to national security because two of his children had attended a mosque associated with a Muslim cleric linked to a suspected terrorist group.
PC Farooq was a firearms specialist working for the Wiltshire Constabulary when he was transferred to the DPG.
Its main role is to provide protection at government, diplomatic and Metropolitan Police sites. All officers within the DPG must undergo security vetting, including a counter-terrorism check (CTC).
PC Farooq had been accepted into the DPG when he was told in December 2003 that he had failed his CTC.
PC Farooq's solicitor, Lawrence Davies, said: "We live in a society where it is possible to point a finger at a Muslim abroad and say that they have WMD and are a threat to national security and no questions are asked.
"Now those who 'protect' us feel emboldened to point the same finger at British Muslims.
"Muslims are labelled guilty by association. Doubt is insufficient to save them. They are assumed guilty before being proven innocent."
Peter Smyth of the Metropolitan Police Federation said the necessary checks should have been carried out before PC Farooq's transfer.
"All police employees should be vetted before they are recruited and given a contract.
"It seems to us a bit perverse to do otherwise. If these checks had been carried out in advance then presumably he would not have been accepted as a transfer from Wiltshire."
Superintendent Dal Babu from the Association of Muslim Police told the BBC that officers, particularly those in sensitive roles, had to go through stringent checks before being assigned their duties.
"There are three levels of security in the police service, and all police staff are required to have a security check at the most basic level and that's reviewed every 10 years.
"In addition to that if you then have access to firearms, or you're protecting diplomats then you're required to have a high level of security."
A Scotland Yard spokesman said: "What we can say is that the decisions that the Metropolitan Police Service have taken in this particular case are entirely proportionate, defendable and justified.
"We carry out appropriate vetting of officers and staff throughout their careers. The level of vetting increases according to the sensitivity of the roles that officers and staff have to perform.
"We have an excellent relationship with the Association of Muslim Police who have recently stated that the vetting process is used appropriately and 'not indiscriminately'."
Another Met officer, Alexander Basha, was excused from guarding the Israeli embassy in Kensington Palace Gardens in central London last month after expressing concern over his family links with Lebanon.