The family of Harry Dunn is to begin legal action against the Foreign and Commonwealth Office (FCO).
The 19-year-old died in a crash outside RAF Croughton with a car owned by US citizen Anne Sacoolas, who later left the UK claiming diplomatic immunity.
Earlier the Dunn family held a meeting with human rights barrister Geoffrey Robertson QC.
Family spokesperson Radd Seiger told Sky News: “The first action we will be taking is against the FCO.”
“We will be shortly issuing a letter of claim which is a prelude to a judicial review,” he added.
The family has also referred Northamptonshire Police to the Independent Office for Police Conduct.
Mr Seiger said: “We are absolutely clear that the Foreign Office’s decision to advise Northamptonshire Police that Mrs Sacoolas had the benefit of diplomatic immunity was unlawful and we will be seeking a judicial review of that decision to have it quashed.”
He also appealed for Mrs Sacoolas “to come back to this country and face the music.”
On Tuesday, Northamptonshire Police Chief Constable Nick Adderley said Mrs Sacoolas would be interviewed under caution in the US.
Officers from Northamptonshire Police are waiting for the necessary visas.
Mr Seiger said Northamptonshire Police had “not disclosed all the information this family are entitled to”.
“We have deep concerns about the manner in which this investigation was conducted, and simply adding insult to injury to this family at their darkest hour,” he added.
Mr Adderley had previously said Northamptonshire Police had at all times “acted with the upmost integrity and transparency”.
Mr Seiger said: “This family have a steely determination about them to ensure that Harry has not died in vain.
“I think the whole nation, the whole world now, is looking at this set of circumstances and it isn’t right.”
Mr Dunn’s motorbike was involved in a collision outside RAF Croughton in Northamptonshire on 27 August. He died in hospital.
Mrs Sacoolas’ husband Jonathan is a US intelligence official who was working at the base at the time of the crash.
Both the British and US governments agree that by returning to the US, Mrs Sacoolas forfeited the right to diplomatic immunity.
Hearts review CCTV to find fan after Zdenek Zlamal coin throw
Media playback is not supported on this device Hearts goalkeeper Zdenek Zlamal is struck with a coin from Rangers endHearts are examining footage to find the supporter who threw a coin at their goalkeeper Zdenek Zlamal in their Scottish Cup win over Rangers.The Czech was hit in the chest by a two-pence piece thrown from…
Hearts are examining footage to find the supporter who threw a coin at their goalkeeper Zdenek Zlamal in their Scottish Cup win over Rangers.
The Czech was hit in the chest by a two-pence piece thrown from the Rangers section of the ground late in the second half with the hosts 1-0 up.
Footage also shows another coin narrowly missing the player as he attempts to take a goal kick.
Daniel Stendel’s side won the game to reach the semi-finals.
It comes a year after Zlamal was targeted with a coin by a Celtic fan at Tynecastle in a 2-1 win for the Glasgow club.
The 34-year-old was also punched in an Edinburgh derby by a Hibs fan, who was given a football banning order for a year and ordered to perform unpaid work.
Police Scotland have been contacted for comment.
Hearts 1-0 Rangers: Hearts goalkeeper Zdenek Zlamal is struck with a coin from Rangers end
Hearts goalkeeper Zdenek Zlamal is struck with a coin from the Rangers end at Tynecastle in the home side’s 1-0 Scottish Cup win.UK users only
Hearts goalkeeper Zdenek Zlamal is struck with a coin from the Rangers end at Tynecastle in the home side’s 1-0 Scottish Cup win.
UK users only
Sophia Florsch: German driver to be in all-female Le Mans 24-hour team
Sophia Florsch is to be the first woman to race in the Formula 3 seriesAn all-female team including Sophia Florsch will compete at this year’s Le Mans 24-hour race. June’s race will take place less than two years after German Formula 3 driver Florsch, 19, survived a huge 170mph crash at the Macau GP, after…
An all-female team including Sophia Florsch will compete at this year’s Le Mans 24-hour race.
June’s race will take place less than two years after German Formula 3 driver Florsch, 19, survived a huge 170mph crash at the Macau GP, after which she needed surgery on a fractured spine.
She will line up with Alfa Romeo F1 test/development driver Tatiana Calderon and Briton Katherine Legge.
They will drive in the LMP2 category for Richard Mille’s Racing Oreca team.
Florsch said on social media: “Yes! I am racing this high class superduper motorsport event. Ready to rumble girls.”
Legge, 39, is an experienced sportscar driver who has competed in the Daytona 24 Hours event in America in all-female line-ups for the past two years.
Calderon, 26, raced in Formula 2 – Formula 1’s undercard series – last season for the Arden team.
They all currently compete in the Oreca car in the European Le Mans Series of endurance racing.
The Le Mans 24-hour race is one of motorsport’s biggest events, which sees many top drivers competing.
Last year’s race was won by a team including two-time F1 world champion Fernando Alonso.
The 2019 event also saw the first all-female line-up compete in the famous race, finishing in 39th place.