Harry Dunn's mum has said Foreign Secretary Dominic Raab is "not fit to hold public office" as she called on voters to kick him out of Parliament at the general election .
Charlotte Charles said she felt "utterly betrayed" by Mr Raab and said she felt he hadn't done enough to bring the woman alleged to have hit her 19-year-old son's motorbike outside RAF Croughton to justice in the UK.
She alleges he misused or abused his power by letting Anne Sarcoolas leave the country.
She said that the family had not "to this day" heard from Boris Johnson about her son's death or the diplomatic row that followed.
It came as Harry's dad Tim Dunn, and step-dad Steve Charles led a group of family members and the teenagers' friends to challenge Mr Raab as he attended hustings in his Esher and Walton constituency on Monday night.
Mr Raab won his seat with a majority of over 23,000 votes at the last election - but the Liberal Democrats are understood to be confident that they could defeat the Brexiteer after an analysis by polling company Datapraxis showed he could be unseated.
A defiant Charlotte, 44, told the Mirror: " Dominic Raab is not trustworthy, the way he has treated our family is unforgivable.
"Our boy's life is worth so much more than just being told by our government to just go away and grieve.
"It feels like a stitch-up behind the scenes and I feel like I have been utterly betrayed."
The family said they feel that they have been misled by Mr Raab.
Charlotte said: “On October 21 Mr Raab said in parliament there were no obstacles to justice, but last week he said he was still working to clear obstacles.
“We believed that meant we would soon be seeing justice move forward, but Dominic Raab just blew that open again.”
Last week Mr Raab said the Foreign Office was “doing everything it can to clear the path for justice for Harry’s family” and allow the police and the Crown Prosecution Service to “do their job”.
However, on 21 October he told the House of Commons: “At every stage in this process we have sought to clear away any obstacles to justice being done … I am currently aware of no barriers to justice in this case.”
Mr Raab has also defended a decision to pursue costs against the family if they lose a pending judicial review.
He told Sky News: "We just cannot responsibly allow ourselves to be sued without taking the normal action in defending ourselves when the position that the representative and the family are pursuing in law is wrong."
He continued: "It pains me because I want to give them the solace of justice in this case.
"But we also need to protect the taxpayers' money and the legal position that we set out, which is the correct one."
Family spokesman Radd Seiger told the Mirror the family are encouraging voters to back Lib Dem candidate Monica Harding
"This isn't about her politics, it is about backing the candidate most likely to beat someone untrustworthy," he said.
Harry Dunn was just 19-years-old when he was killed in a collision outside RAF Croughton in Northamptonshire in August.
The car was being driven by the wife of a US intelligence officer, Anne Sarcoolas.
The mum-of-three later left the country with permission from the FCO and has refused to return. But the government later admitted that Ms Sarcoolas, 42, did not have diplomatic immunity, but the United States has given no indication that they will return her to the UK if she is prosecuted.
Charlotte said Mr Raab's conduct had left her unable to trust him and in a plea to people in his seat she told the Mirror: "He has misled us and it is unforgivable.
"I just can't see how anyone in the constituency can trust him to do anything or to stick to his word.
"You want someone you can rely on as your MP - and he isn't that."
The family confirmed that the family would file an application for a judicial review into how the FCO's decision - despite what the family see as "threats" to pursue them for costs.
A letter to the family read: "In the event that the claim is issued, it will be defended, the application for permission will be opposed, and the secretary of state will seek his costs for doing so."
Northamptonshire Police earlier this month handed over a file of evidence to the CPS after conducting an interview with the Ms Sarcoolas in the US, a decision on charges is yet to be made by authorities.
