The family of Harry Dunn have been told the Foreign Secretary was unaware of the teenager’s death until after suspect Anne Sacoolas had left the country.

The Foreign and Commonwealth Office (FCO) said Dominic Raab was personally made aware of the case only after Sacoolas’s departure on September 15 – 19 days after the fatal road crash.

This is despite a briefing note, copied to Mr Raab’s private office three days after Mr Dunn’s death, which revealed concern for “very unpalatable headlines” over the suspect’s claim to diplomatic immunity.

It also previously emerged that a text message was sent by a senior diplomat at the FCO to their US embassy counterpart saying they should “feel able” to put Sacoolas on the next flight home.

A request for the suspect’s immunity to be waived was declined by the US on September 13 – at least two days before Mr Raab was made aware of the case.

The FCO informed the family about the Foreign Secretary’s late introduction to the case on Tuesday – more than nine months after Mr Dunn’s death.

Sacoolas, 42, the wife of a US intelligence official based at RAF Croughton in Northamptonshire, was charged with causing death by dangerous driving in December last year.

An extradition request, submitted by the Home Office, was rejected the following month – a decision later described by the US State Department as “final”.

Mr Dunn’s mother, Charlotte Charles, said Mr Raab’s late introduction to the case had never been mentioned to the family before Tuesday evening.

She told the PA news agency: “We have met with Dominic Raab and his advisers numerous times yet never once did they mention that he did not have control of the situation last September, that he just did not know about it until after Mrs Sacoolas left.

“That just can’t be right. But if it is, why have the FCO left it to the 11th hour to say that the captain of the ship was off somewhere else while the ship was burning?

“Why after all our meetings did they not tell us that and just offer it up to us now?”

Mrs Charles added: “The man just cannot be trusted.

“He owes us a duty of candour which he has never once complied with. We only wanted the truth from him, nothing else.

“Whether he knew or not, and I refuse to believe he didn’t know, he has to resign or be sacked.”

Commenting on the email from the FCO, the family’s spokesman Radd Seiger told PA: “It is utterly inconceivable that Mr Raab was unaware of Harry until after Mrs Sacoolas had gone.

“We know his private secretary received a detailed note about the case on August 30.

“We know that she was being kept abreast of developments.”

Mr Seiger continued: “Every senior member of Mr Raab’s team was aware of what was going on, anticipating that there would be unpalatable headlines.

“If he really did not know despite all that, we are going to have accept that his entire leadership team kept one of the most important cases away from their boss.

“If true, then what does that say about his control over his ship and his relationship with his team?”

A spokesman for the FCO said: “We have the deepest sympathy for Harry’s family. No family should have to experience what they have been through.

“The case remains of the highest priority for the Foreign Secretary, who continues to raise the case with the US government.

“Both the Foreign Secretary and the Prime Minister have been clear with the US that the refusal to extradite Anne Sacoolas amounts to a denial of justice, and that she should return to the UK.

“The Foreign Secretary remains ready to meet Harry’s family and to support them to get the justice they deserve.”

It is understood the FCO remains confident it has acted properly and lawfully in relation to Mr Dunn’s death.