The parents of Harry Dunn have vowed to continue their fight after a White House meeting in which Donald Trump told them the US woman allegedly responsible for their son's death would not return to the UK.
Anne Sacoolas left the UK after the crash in Northamptonshire which killed the 19-year-old in August.
After their meeting with the US president, the family's representative Radd Seiger said "the search for #Justice4Harry continues".
The teenager's parents said they had refused to meet Mrs Sacoolas who was also in the White House on Tuesday.
READ MORE: US woman in crash case involving British boy ‘does not have immunity’
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Charlotte Charles and Tim Dunn said after their meeting with Mr Trump in the Oval Office that there had been "a little bit of progress".
Ms Charles said: "We didn't get the answers that we wanted.
"They couldn't tell us who made the decision to bring her back to the US. We asked how long she was there for and they still said three weeks."
Asked if she felt the meeting was trying to sweep Harry's death under the carpet, Ms Charles said: "Initially yes, I did think they were trying to do that - certainly by having Mrs Sacoolas there.
'It's just not enough'
"I think maybe they were thinking that would be enough for us. We're seven weeks on and it's just not enough."
Mr Dunn said of turning down the chance to meet Mrs Sacoolas at the White House: "We weren't ready to meet her, it would have been too rushed.
"It's not what we wanted - we wanted a meeting with her in the UK."
But he added that the meeting "didn't feel like a stunt - they didn't try and force it on to us".
Ms Charles added: "But I don't think it would be appropriate to meet her without therapists or mediators in the room."
Their campaign has attracted interest on both sides of the Atlantic due to the chief suspect being the wife of a US diplomat stationed in the UK.
Mrs Sacoolas has previously said she was "terribly sorry" about the incident and had "no time to react" when she saw Mr Dunn's motorbike near RAF Croughton on August 27.
In a post on the Justice 4 Harry GoFundMe page, Ms Charles and Mr Dunn said of the meeting at the White House: "We are grateful for the invitation, which we hope represents a positive development in our fight for justice.
"Our priority, as any parent will understand, is justice for our child. We believe this can only be achieved if Anne Sacoolas returns to England and engages properly with the justice system, where she will be treated fairly in a proper investigation of what happened to our son on that day - an investigation that cannot happen without her co-operation.
"Friends tell each other the truth. If Britain and America are friends then we believe there should be no possibility of a citizen of one country hiding from justice in another while falsely claiming a privilege such as diplomatic immunity."
The family, who met Foreign Secretary Dominic Raab in the UK last week, have also demanded an investigation into the Foreign Office's (FCO) advice to Northamptonshire Police that Ms Sacoolas had diplomatic immunity.
They are demanding to see all emails, messages and notes sent in relation to her status.
Mr Seiger said: "We want to conduct an investigation into the FCO's decision to advise Northamptonshire Police that this lady had the benefit of diplomatic immunity.
"What we don't know is whether somebody cocked up or whether they were put under pressure by the Americans to concede."
Mr Seiger added: "If we're not satisfied, then we'll go to a judicial review and ask a High Court judge to review it all."
On Saturday, before the family left for the US, they received a letter from Mr Raab, saying that Mrs Sacoolas, 42, no longer had immunity.
"The letter is worded very carefully, they're not saying it's just a change of heart - they are saying that it's an evolution," said Mr Seiger.
He also said that the family's lawyers, Mark Stephens and Geoffrey Robertson QC, believe "they've (the FCO) been lying to you".