The Shoreham air disaster was caused by the pilot flying too slow and too low during a loop manoeuvre, accident investigators have said.

Eleven people were killed and 13 injured on August 22, 2015, when Andrew Hill, 52, smashed a vintage jet onto the A27 in West Sussex during an air show.

The speed that the 1955 Hawker Hunter entered the manoeuvre was too low and it failed to use maximum thrust, the final report by the Air Accidents Investigation Branch (AAIB) stated.

It also concluded that measures taken to mitigate the effects of an aircraft crashing outside the boundary of the air show were "ineffective" and contributed to the severity of the incident's toll.

Responding to the report, the parents of victim Matthew Grimstone, 23, said the Civil Aviation Authority (CAA) and the air show organisers "have got much to answer for".

In a statement, they said: "Apart from anything that the pilot may have got wrong, it is very evident the CAA and the Shoreham Air Show organisers have got much to answer for.

"Rules laid down by the CAA were quite clearly inadequate and those that were there were, in some cases, not fully adhered to by the air show organisers."

Mr Hill, from Sandon, Hertfordshire, suffered serious injuries and is being investigated by Sussex Police for possible manslaughter.

Following the publication of the AAIB report, the force said it hopes to submit a file of material to the Crown Prosecution Service (CPS) by June 20.

Flight trials indicated the former Royal Air Force pilot could have pulled out of the stunt up to four seconds after reaching the top of the loop, but he either did not perceive it was necessary or did not realise it was possible.

He had not received formal training to escape the manoeuvre and had not had his competence to do so assessed, the report found.

The speed, height and thrust followed in the Hunter were "very similar" to a Jet Provost that the pilot had flown during displays in the run up to the Shoreham event, AAIB principal inspector Julian Firth said.

He added that it was possible "the pilot recalled the wrong numbers, essentially mixing up the two aircraft".

Mr Hill was interviewed on seven occasions by AAIB investigators, but he could not remember events between the evening of August 19 and regaining consciousness in hospital after the accident.

He was able to describe his normal practice, but not the events on the day of the crash.

The pilot was attempting a bent loop, in which the aircraft pitches up into a loop and then rolls before leaving the manoeuvre in a different direction to its entry.

His display authorisation permitted him to carry out aerobatics at a minimum altitude of 500ft and the normal technique would be to enter the loop at an airspeed of at least 350 knots and use maximum engine thrust to achieve a height of at least 3,500ft at the apex.

But Mr Hill began the stunt at 185ft and a speed of 310 knots, reaching 2,700ft at the top of the loop.

Cockpit footage during the flight showed Mr Hill "alert and active", with no suggestion he had passed out, investigators said.

Detective Chief Inspector Paul Rymarz said officers will now begin looking at the AAIB's report with their independent experts.

He said: "We have been waiting some time for this report and it will take us some time to review.

"Our progress has been dependent on this final report and as a result of the ruling in the High Court, much of the material contained in it has not been seen by the investigation team until now."

He added: "We remain committed to finding answers for the families and friends of those who died."

Organisers of the Shoreham air show said it was unlikely they will stage "the same or similar style event" in the future.

The AAIB made a total of 32 safety recommendations for the CAA, including 10 in the final report.

The CAA said it would act on them "as a priority".

Safety rules at UK air shows were tightened in the wake of the Shoreham crash.