The family of motorcycle crash victim Harry Dunn (pictured) have called for a chief constable to quit over 'outrageous' comments he posted on social media

The family of motorcycle crash victim Harry Dunn have called for a chief constable to quit over 'outrageous' comments he posted on social media.

Earlier this week, Harry's parents revealed they would be taking legal action in the US against Donald Trump and Anne Sacoolas, the American driver of the car that hit their son, 19.

Responding to a tweet about the development, Northamptonshire chief constable Nick Adderley wrote: 'How sad but how predictable!!'

It is understood the message remained online for less than ten minutes before Mr Adderley deleted it but Harry's family said in a statement: 'It is totally outrageous and absurd for him to take sides and it is clear now that he is just against us. We are so angry at him. We are calling on him to resign immediately.'

They say a civil case in the US is their only hope of getting justice.

Mr Adderley said the tweet was in reference to the 'profound sadness at the loss of Harry Dunn' and the fact that his family now felt the 'only recourse to justice that they feel they have available to them at the moment is through the US civil court system'.

He added: 'I deleted it with a view to rewriting it with more context but was called away to deal with something else. I meant no offence by my tweet and apologise.'

Meanwhile, detectives investigating Harry's death in the head-on crash have questioned diplomat's wife Mrs Sacoolas in the US, paving the way for a prosecution.

Northamptonshire Police said details would now be passed to the Crown Prosecution Service to decide whether to press charges, including causing death by dangerous driving, against the suspect.

Responding to a tweet about his parents' legal action in the US, Northamptonshire chief constable Nick Adderley (pictured) wrote: 'How sad but how predictable!!'

It is understood the message remained online for less than ten minutes before Mr Adderley deleted it

That may lead to Mrs Sacoolas facing extradition. The 42-year-old mother of three has admitted being on the wrong side of the road when she hit Harry's motorbike outside RAF Croughton in Northamptonshire on August 27.

She spoke to police at the scene but later fled the country, citing diplomatic immunity because of her husband Jonathan's role at the base, a US spy hub.

Harry's parents Charlotte Charles, 44, and Tim Dunn, 50, insist she does not have diplomatic immunity, describing her as a fugitive.

Mrs Sacoolas – who is understood to be in hiding on a US military base – had indicated she would be willing to speak to British officers under caution. But Mrs Charles said: 'Why should our UK taxpayers be funding the police to go to the States when ideally, really, she should have been coming back here?'

Harry's family said in a statement: 'It is totally outrageous and absurd for him to take sides and it is clear now that he is just against us. We are so angry at him' (Pictured: Harry's mother Charlotte Charles and father Tim Dunn, right)

Last night Mr Trump risked angering Harry's family further when he said Mrs Sacoolas had a 'compelling story to tell' when he met her at the White House. Mr Trump said he had tried to broker a meeting between her and Harry's family so they could 'grieve together' but his parents refused, calling it a 'stunt'.

In an LBC radio interview with Nigel Farage, Mr Trump said: 'I was in the Oval Office with the parents and the young lady was in a room right next to the Oval Office, but the parents decided, in their wisdom, and it is certainly their choice, not to see her.

'I can understand that too.'