The first ever derailment on Croydon's tram network was caused primarily by a track circuit failure, an investigation has found.

The tram came partly off the tracks at East Croydon stop on February 17 last year after the electric current that locks the vehicle to the rails failed, a report by the Rail Accident Investigation Branch (RAIB) concluded.

It caused the centre and rear of the tram, which was travelling at 7.5mph, to be sent on a different path from the front. 

Around 100 people were led to safety after the incident at 6.23am. No injuries were reported. 

The track concerned, which leads to the second platform at the stop, has not been used since the accident.

RAIB's investigation discovered that silt was present on the track's rail head, suggesting that contamination was also a causal factor of the derailment. 

The report also found that the integration of the tram system was "inadequate" because the need for integrated track circuits and tyre-to-tyre wheel resistance were not communicated to maintenance staff when Tramlink was commissioned.

The track's voltage had not been adjusted to manufacturer Bombardier's instructions, the report added.

RAIB recommended that Tramlink should review track circuit settings and signalling arrangements at East Croydon to consider the system was overly reliant on the track circuit.

It added that TfL should identify areas on the tram network where silt collects and implement at cleaning regime to prevent dangerous build-ups affecting the track.

Sharon Thompson, director of Tramlink, said: "London Tramlink has an excellent safety record and the safety of passengers and staff is always our first priority.

"This incident occurred due to a number of contributory factors as described in the report, coming together at the same time. There is nowhere else on the network where all these things could come together in the same way.

“As an interim measure and to prevent this sort of incident happening again, the track leading to East Croydon platform two has not been used since the incident.

"We are working with the points manufacturer on a solution."