Dominic Raab has admitted the Foreign Office asked Northamptonshire Police to delay telling Harry Dunn's family that the woman involved in the crash that killed their son had left the UK.
Anne Sacoolas is married to a US diplomat, and since leaving the country, admitted hitting the teenager - who was riding a motorbike - when driving on the wrong side of the road.
Mr Raab admitted the Foreign Office had asked for a delay of "a day or two, no more than that" to make sure they were clear on their plans going forward.
However he said the responsibility for telling Harry's family ultimately fell on Northamptonshire Police.
He said: "The police are in charge of liaising with the family at this very difficult and tragic case.
"They asked the Foreign Office for advice and one of our officers said it would be useful to have a day or two, no more than that, just to make sure we were clear on what we'd be doing going forward, and just to make sure that ministers could be consulted.
"Obviously we want to get the information to the family as quickly as possible, and we also want to make sure we have answers for them because ultimately that is very frustrating."
He added: "After that the delay that occurred was the responsibility of the police and I know that throughout this, they've wanted to handle this as sensitively as they can with the family, given the anguish they're going through."
When asked to confirm who was responsible for the delay, Mr Raab added: "Well the police are ultimately responsible for liaising with the family and they take the judgement call... they would have had their reasons for that.
"The question that is being put to us, fairly, is that whether we were responsible for the delay. One of my officers said they wanted a day or two to make sure they were clear on the action we'd be taking next so they could inform and consult ministers."
After it emerged that authorities had delayed in telling the family about Sacoolas’s departure from the UK, Harry's mother, Charlotte Charles, told ITV News: “It’s disgusting. They’ve got to answer some questions we throw at them haven’t they? Because who made that ridiculous decision?”
Harry’s father Tim said: “Dominic Raab said to us when we had that meeting that they and the police were two separate things.”
Charlotte called on the Foreign Secretary to answer the family’s questions. She said: “He needs to do the right thing as well doesn’t he and own up to why they made that decision. Why keep us in the dark? Why add more pain?”
The accident which killed Harry Dunn happened on August 27. Police visited Ms Sacoolas at her home the next day. Officers were told she had left the country on September 16. But Harry’s family say they were not informed by police until ten days later.
Officers have stated the delay was in part due to Harry’s funeral and they are determined to pursue justice. They declined to comment on the allegation that they were asked by the Foreign Office to delay telling the Dunn family about Anne Sacoolas’s departure.
On Tuesday Ms Sacoolas’s lawyers said in a statement about the family’s departure from the UK. “Our understanding is that the British authorities were informed and aware of their departure before they returned to the US.”
A source close to Ms Sacoolas has told ITV News the diplomats wife says she was “pushed” to leave the UK.
Lawyers for Harry Dunn’s family have asked the Foreign Office for emails and documents relating to the case. They say they’re willing to pursue a judicial review if they don’t receive them.
Northamptonshire Police declined to comment.