The wife of a US intelligence officer charged with causing the death by dangerous driving of the 19-year-old motorcyclist Harry Dunn, will not return to the UK voluntarily, her lawyer has announced.

A statement from the lawyer for Anne Sacoolas came after the Crown Prosecution Service announced it was bringing charges over Dunn’s death in August. Amy Jeffress said the potential 14-year sentence was “not proportionate” for what was “a terrible but unintentional accident”.

The statement said: “Anne is devastated by this tragic accident and continues to extend her deepest condolences to the family. Anne would do whatever she could to bring Harry back. She is a mother herself and cannot imagine the pain of the loss of a child. She has cooperated fully with the investigation and accepted responsibility … This was an accident, and a criminal prosecution with a potential penalty of 14 years’ imprisonment is simply not a proportionate response.”

Jeffress said they had been talking to the UK authorities about how Sacoolas could “assist with preventing accidents like this from happening in the future, as well as her desire to honour Harry’s memory … But Anne will not return voluntarily to the United Kingdom to face a potential jail sentence for what was a terrible but unintentional accident.”

Facebook Twitter Pinterest Anne Sacoolas pictured pulling out of her driveway in the US earlier this month. Photograph: ITV News/PA

Sacoolas was flown out of the UK by the US embassy days after the fatal collision , with the US claiming she was covered by diplomatic immunity,

A file on the evidence was handed to the CPS on 1 November and there has been no dispute that Sacoolas was driving a car on the wrong side of the road when it hit Dunn.

The chief crown prosecutor, Janine Smith, said: “Following the death of Harry Dunn in Northamptonshire, the Crown Prosecution Service has today authorised Northamptonshire police to charge Anne Sacoolas with causing death by dangerous driving.

“May I remind all concerned that criminal proceedings against Anne Sacoolas are now active and that she has a right to a fair trial. It is extremely important that there should be no reporting, commentary or sharing of information online which could in any way prejudice these proceedings.”

The CPS said it had started extradition proceedings.

It said: “The Home Office is responsible for considering our request and deciding whether to formally issue this through US diplomatic channels”

The US Department of State said the CPS statement was “disappointing and will not bring a resolution closer”. It reiterated that it believed Sacoolas had diplomatic immunity. A department spokesman said: “The use of an extradition treaty to attempt to return the spouse of a former diplomat by force would establish an extraordinarily troubling precedent.”

Sacoolas had been in the UK for only three weeks when the crash occurred. She has been interviewed by British police in the US.

Harry’s family have been fighting a drawn-out legal and political battle on both sides of the Atlantic to force Sacoolas to come back to the UK to face charges.

Sky News filmed the Dunn family at home on Thursday in tears when they heard of the CPS decision. Tim, Harry’s father, said: “We believed. We have done it. We have got the charge. It’s amazing. It does not matter what happens now.”

Charlotte Charles, Harry’s mother, said she had made a promise to get justice for her son. “I would never have rested properly unless I carried out that promise.”

Facebook Twitter Pinterest Harry Dunn died when his motorbike was hit outside RAF Croughton on 27 August. Photograph: Family handout/PA Media

Sacoolas went to the White House when the Dunn family were meeting Donald Trump, and was waiting in a different room for Trump’s instruction to meet them. The family declined the invitation, which was extended to them without warning.

The claim of diplomatic immunity has been disputed by lawyers acting for the family. They assert Sacoolas is the wife of an intelligence officer and the Northamptonshire RAF Croughton base is in reality a US intelligence listening base. The Foreign Office says the base was listed in 1964 as an annex of the US embassy and that its staff have immunity. It also claims her immunity lapsed once she was back in the US and she should do the right thing and return to the UK.

The extradition issue will be, in the first instance, a matter for Nick Adderley, the chief constable of Northamptonshire police. On Friday, he said hoped the US authorities “would see sense and see the injustice in this case”. He said Sacoolas “will have to live with what has happened and it may do her a world of good for her own mental health to come back and face whatever justice decides”.

The foreign secretary, Dominic Raab, is to start talks with the US to end an anomaly whereby family members of US staff based at RAF Croughton appear to have greater protection than the staff themselves. On Friday he welcomed the charging decision, but said it did not represent the end. “I hope Anne Sacoolas will realise the right thing for her to do is to come back to the UK and co-operate with the criminal justice process.”

The precise work of staff at RAF Croughton has not been disclosed, and the decision to remove Sacoolas and her family from the UK looks to have been linked to a thwarted US desire to minimise publicity about the base as a US intelligence communications hub.

Under arrangements agreed in 1964, US staff members at the base “pre-waived” their immunity against criminal prosecution in the UK, but this was not done for their families. The Foreign Office has rejected freedom of information requests on the terms of the 1964 agreement saying it is not in the national interest.

One option being explored is to extend this automatic waiver to family members so their degree of protection is the same as for staff.