The family of Harry Dunn have said they suspect the British government of colluding with the United States to "cover up" details of his death and renewed calls for police to extradite Anne Sacoolas, the wife of a US intelligence agent accused of killing him.
Radd Seiger, a spokesman for the family, said: "The search for justice has now expanded beyond simply Mrs Sacoolas' return, as important as that is.
"The family is now concerned that there has been misconduct and a cover up on both sides of the Atlantic and they are intent on exposing it."
The call came after Dominic Raab, the Foreign Secretary, admitted the Foreign and Commonwealth Office asked police to delay informing the family that Mrs Sacoolas had left the country.
Speaking on Good Morning Britain, Mr Raab said: "I know there was a delay and we were asked our opinion by the police, and I think an official from the Foreign Office said it would be helpful to have a day or two.
"I know the police delayed a bit longer, and they are responsible for that."
He added: "We have done everything we can within the law to clear the path so that justice can be done for the family and we will continue to do so."
Mr Raab was speaking after ITV News reported there had been a been a ten-day delay between officers learning that Mrs Sacoolas had left the country and the family being told.
Charlotte Charles and Tim Dunn, Harry's parents, told the Telegraph they felt that the British government had abandoned them, saying they believe the Foreign Office “just want us to go away and forget about it all”.
“We don’t understand why,” said Mr Dunn. “Harry has died in an accident, and we feel that nobody but us wants to get justice for him.”
They were due to fly back from the United States on Friday after a five day trip to plead with US officials to send Mrs Sacoolas back to the UK.
The trip included a surprise meeting with Donald Trump at the White House, which the family say ended after he suggested an impromptu photo-opportunity meeting with Mrs Sacoolas in the Oval Office.
Mr Seiger said when they said they would only meet her on UK soil, Robert O’Brien, Mr Trump's national security adviser, said she would never return to Britain.
Mrs Sacoolas is alleged to have been driving her right-hand drive Volvo on the wrong side of the road when her car hit Mr Dunn, who was riding his motorbike, on August 27.
She and her husband Jonathan Sacoolas, a US intelligence officer, were spirited out of Britain on a private flight from a US air base after the incident.
The 42 year old mother-of-three, claimed diplomatic immunity to avoid prosecution despite not being on the official London diplomatic list.
The Foreign Office confirmed however that Mrs Sacoolas and her husband, 43, were given diplomatic immunity prior to their arrival in the UK under the Vienna Convention.
The immunity is extended to intelligence officers and other Americans working on military bases including RAF Croughton in Northamptonshire where the crash happened.
Mr Seiger said the family did not accept that Mrs Sacoolas had diplomatic immunity and would be meeting with the chief constable of Northamptonshire police next week.
The family has called on the force to charge Mrs Sacoolas and initiate extradition proceedings.
Mr Seiger said he the family had told the FCO and US officials that they were prepared to "have a conversation" if there were security concerns related to Mr Sacoolas' work, but had been rebuffed.
"If there is some good reason why this lady should have been recalled, the family would have been open to that discussion. But they just completely ignored us," he said.