Police leaders have warned they will tell officers to let violent suspects go if they do not have broader support following an attack on a female PC.

Ken Marsh, chairman of the Metropolitan Police Federation, said if officers were going to get assaulted for simply doing their job, then it was not worth putting themselves at risk.

He spoke out after video footage emerged of two officers locked in a violent struggle as they tried to make an arrest in Merton, south London, on Saturday.

A female police officer was filmed being kicked in the head during the routine traffic stop, before being left lying dazed in the road clutching her head just feet away from a passing bus.

Her male colleague was dragged around in the road as he tried to stop a suspect in a white tracksuit from running away.

The female officer had tried to use incapacitant spray on the pair but to no effect.

Both were hospitalised following the attack, treated for head injuries and cuts.