The withholding of information about the death of motorcyclist Harry Dunn outside a US military base caused “distrust” among his family of the authorities, an independent review has found.

The 19-year-old was hit by a car being driven on the wrong side of the road by Anne Sacoolas at RAF Croughton in Northamptonshire in August 2019.

The US State Department employee had immunity from prosecution and was allowed to leave the country on 15 September, but the family were not officially informed until 11 days later.

Foreign Secretary Yvette Cooper said the government was “committed to the learning the lessons from this tragedy”.

In her report into the actions of the Foreign, Commonwealth and Development Office (FCDO), review chairwoman Dame Anne Owers said there were “failings and omissions”.

She said Mr Dunn’s family was not officially told of the driver’s name, her immunity and that she had left the country until 26 September.

The report noted that Mr Dunn’s father was already aware Sacoolas’s children had left the country, because he was head of maintenance at their school.

“This understandably created distrust both of the message and the messengers,” she said.

“The belief that there had been a conspiracy between the UK and US authorities to secretly ‘spirit her out’, with information deliberately withheld from the family.”

The report, published earlier, examined actions taken by the FCDO between the teenager’s death on 27 August and the end of December 2019.

A police inquiry concluded that Sacoolas was not arrested at the scene because she was deemed to be in a state of shock and it was not deemed necessary at the time.

Dame Anne’s report explained that she was a US State Department employee, but had diplomatic immunity at the time because she was the wife of a US intelligence officer.

The then-foreign secretary was not told the family had left the UK until the following day, said Dame Anne.

Meanwhile, Northamptonshire Police was not told by the FCDO that Sacoolas’s diplomatic immunity was possible until she was back in the US.

After Sacoolas’s departure, Dame Anne said the FCDO asked police for a “day or two” to “get our ducks in a row” before informing family.

The department then asked police not to mention its request – regarding the delay – when the force met the family on 26 September.

Sacoolas pleaded guilty to causing death by careless driving in 2022 and was given an eight-month suspended jail term.

Dame Anne recognised that the Protocol Directorate – the FCDO department responsible – was under “huge pressure”.

She made a series of recommendations for the FCDO, including:

• An “immediate surge of resources” with “early ministerial involvement” when responding to exceptional circumstances
• A strategy to communicate and engage with families and victims
• The skills and experience of consular staff should be deployed when needed in sensitive cases involving diplomats in the UK

“The issue was not recognised as a crisis and escalated to a sufficiently high level at an early stage, losing opportunities to influence, rather than respond to, events,” said Dame Anne.

“Direct communication with the family was late, sporadic and often overtaken by events, and the FCDO was slow to recognise that the family were allies in achieving justice and securing other necessary changes.”

The Conservatives were in office at the time of Mr Dunn’s death.

The loophole, which meant Sacoolas had diplomatic immunity, was closed in 2020.

Dame Anne’s report praised the family’s Justice4Harry campaign and said the FCDO was “slow to recognise that the family were allies in achieving justice and securing other necessary changes.”

In a statement, Mr Dunn’s mother Charlotte Charles said the review had been “a hugely emotional experience” that “triggered a lot of anger”.

“Having turned to the authorities for help, we got nothing from them,” she said.

“The report confirms what we have lived with every day for more than six years, that mistakes were made, that opportunities were missed, and that our family was not treated with the honesty or urgency that any grieving parent deserves.

“Nothing will bring our beautiful Harry back, but today we feel seen, heard and believed.”

Mr Dunn’s father Tim Dunn said: “The hardest part is knowing that more could and should have been done for our boy in those early days.

“The lack of escalation, the confusion, the silence; it all made our loss so much harder to carry.

“What matters now is that lessons are learned. We expect every recommendation to be implemented so that no other family has to fight like we did.”

Cooper said she accepted the recommendations in full, and she shared her “huge respect for the dignity and resolve Harry’s family has shown throughout the period since his tragic death”.

She said: “No family facing a crisis of this kind should have to fight for the support they rightly deserve.”