Three motorcycle gardai from the Regional Traffic Unit based at Dublin Castle were escorting a taxi taking a man to the Mater Hospital when an official patrol car joined them at the Chapelizod bypass on the N4.

The driver of the car was based at a Dublin garda station and was on his way to Kilmainham district court at around 1.40pm.

He joined the back of the escort without being asked or being authorised to do so and one of the motorcyclists waved to indicate that his presence wasn't required.

The garda car is then alleged to have gone up the outside of the last motorcyclist and forcibly rammed into the side of the motorbike, forcing the driver towards the central crash barrier.

The garda suffered a leg injury and was out of work for six weeks. His colleagues in the escort continued towards the Mater but were aware an incident had occurred.

Words were exchanged between the two gardai involved and the injured man made an official complaint.

The injured garda, his two colleagues and the taxi driver all gave statements during an internal inquiry, but the officer accused of the ramming incident declined to make any statement explaining his actions.

He was not suspended but has since been transferred.

The incident occurred at the end of March and a file was sent to the DPP last month.

It was recommended he be charged with dangerous driving and a charge of reckless endangerment could also result.