The controversy over alleged racism in Britain’s largest police force has deepened after it emerged that an officer of inspector rank has been arrested on suspicion of racist abuse.

The Metropolitan police said the inspector, who is based in north London, was arrested by officers working in the force’s complaints department on Tuesday. He has been suspended.

The incident in which he is accused of using racist abuse occurred in Barnet, at 7.40am on Monday, while the inspector was off-duty.

He is the highest ranking Met police officer to be placed under investigation since the latest controversy over racism engulfed the force.

It is the 13th case of alleged racism by Met police officers to emerge in the past four weeks. In total, 27 police officers are now under investigation or facing prosecution over alleged racism.

Some were investigated after complaints from members of the public about the use…