Australia regained the urn on Monday when they polished off Joe Root's side to win the third test at the WACA by an innings and 41 runs and take a 3-0 lead in the five-match series.
All England have left to play for is pride in Melbourne and Sydney, but Overton says the series is not over as they try to halt an eight-match losing sequence in tests in Australia.
"We have not been good enough for long enough in this series and have let chances slip, and because of that we have lost the Ashes before Christmas," he said in The Times on Tuesday.
"We are gutted but don't for a second think that there will be divisions in the camp or that we see the series as over.
"We will be throwing everything we have at the Melbourne and Sydney Tests -- we are desperate to make a mark on the series, even if it's too late to win.
"We will fight until the very last to do so."
Whether or not Overton will be fit to play a part is another matter entirely after he suffered a hairline fracture of a rib while diving in the field at Perth.
"I am nursing a hairline fracture to my rib but the doctor warned me it could become much worse if I landed the wrong way -- a proper fracture, or even a punctured lung. No one needs that," Overton said. "I've been brought up to fight through the pain, and I'm not the sort to leave the field for nothing."
Somerset seamer Overton enjoyed a dream start to his test career when he picked up the wicket of Australian captain Steve Smith in the second test in Adelaide.
With six wickets to his name in his two tests and an impressive 41 not out with the bat in Adelaide, Overton was one of the few England players to emerge with much credit.
He said he is desperate to play in the Melbourne test which begins on Dec. 26.
"I won't rule myself out of Melbourne. I accept it's unlikely, but I'm so desperate to play that I won't accept I'm not going to until the doctors tell me absolutely otherwise.
"I'll be weaning myself off the strong painkillers, just a few paracetamol to help me sleep.
"And no golf! It'll be beach time for me."
First Published: December 19, 2017, 6:02 PM IST