Jenkins, 40, told a jury at Lewes Crown Court yesterday he did not murder 13-year-old Billie-Jo and rejected prosecution claims that he did nothing to help her, despite believing she was alive.
He told the jury of eight men and four women that his "world collapsed" when he found Billie-Jo's body on the patio of the house in Hastings, East Sussex.
Jenkins denies murdering Billie-Jo with a metal tent spike, as she painted the patio doors of the family home on February 15 last year.
He was spending his third day in the witness box being cross-examined by Camden Pratt, QC, prosecuting, over his version of events.
The court heard how Jenkins' older natural daughters Annie, 12, and 10- year-old Lottie, found Billie-Jo's bludgeoned body after they returned from a shopping trip with their father.
The jury heard how, on finding Billie-Jo's body, Jenkins first took Annie and Lottie from the patio into the playroom and stayed with them, rather than helping Billie-Jo.
Mr Pratt asked Jenkins three times how he had helped Billie-Jo, who had terrible head injuries.
Jenkins said: "I went down to her and whispered to her gently and I don't know what I did next."
He said his mind was "spinning" when he found his foster daughter.
Jenkins said: "I was not sure I knew it was not an accident. I could not accept that Billie-Jo had been murdered."
He was also questioned about his 999 call for an ambulance, when he told the operator he had not checked to see if she was breathing.
"When I found Billie, my world collapsed and I do not know if I saw breathing. I have no recollection," he said.
Jenkins was asked by Mr Pratt why he had lied in a second 999 call, saying he had put Billie-Jo in the recovery position when he had not.
He asked Jenkins again why he had not stayed with his foster daughter before emergency help arrived.
"Didn't your natural human care for another human being mean you would want to go straight back to tend an injured person?" asked Mr Pratt.
Jenkins said: "I don't know why I behaved in the manner I did. I had Billie dying on one side of the house, the children on the other crying and screaming and I was running between the two and I panicked."
Mr Pratt said: "There was no point in the recovery position because you knew Billie-Jo was dead." Jenkins replied: "That's just wrong."
After phoning for an ambulance, Jenkins shut the door on Billie-Jo's body and waited in the playroom for paramedics.
The prosecution claims he murdered Billie-Jo as Annie and Lottie waited by the front door, expecting to wash his MG car.
The trial continues today.Reuse content