The Portsmouth girl and woman, 43, died on Thursday, February 19 with police today confirming the deaths.
They were travelling southbound on the A3 just after the tunnel at 10am during half term when they crashed in a red Ford Fiesta.
A police spokesperson said: “It was reported a red Ford Fiesta left the carriageway. The two occupants – a 43-year-old woman and a seven-year-old girl, both from Portsmouth – were both sadly pronounced deceased at the scene.
“We would like to thank motorists for their patience as the A3 southbound was closed for several hours before it could be reopened.
“We would like to speak to any witnesses and in particular anyone with relevant dash cam footage of the incident or the moments leading up to it.
“If you have any information, please call 101 quoting reference 44260083669.”
 See hampshire.police.uk to give information.