Ian Huntley choked back tears yesterday as he told his Old Bailey trial that he accepted he was responsible for the deaths of Holly Wells and Jessica Chapman - but denied it was murder.

He said he was ashamed at what he had done, and admitted deliberately trying to cover his tracks by destroying forensic evidence linking him to the deaths of the ten-year-olds and lying to police.

Prompted by his lawyer to tell the jury how he felt now, he said: "I just wish none of this had ever happened.

"I am sorry for what's happened, I'm ashamed of what I did and I accept I'm responsible for the deaths of Holly Wells and Jessica Chapman, but there's nothing I can do about it now.

"I sincerely wish there was."

The 29-year-old was giving evidence on the first day of his defence case in the 20-day murder trial.

He was in the witness box for about three-and-a-half hours and spoke in a faltering, hushed voice, sometimes shaky and barely audible as he described the events of August 4 last year, when he admits the girls died in his care.

The Soham Village College caretaker said he contemplated suicide in the days after the girls' deaths and tried to kill himself in prison while waiting for his trial.

He told the jury: "I made my mum and dad a promise that I would get myself through to the trial and tell Holly and Jessica's parents what actually did happen."

Huntley said he could not remember how the girls died until he attempted to take an overdose in prison in June this year. His memory then began to return.

The first recollection was of Jessica's voice, screaming "You pushed her, you pushed her", which he said was what she screamed after Holly fell into a bathful of water at his house, 5 College Close, in Soham, Cambridgeshire.

Huntley said he allowed the two friends, wearing their matching Manchester United tops, into his three-bedroom home on Sunday, August 4, last year because Holly had a nosebleed.

Holly sat on the edge of his bath, which had six to eight inches of water in it from a bath he had run for his dog, he said.

He lost his footing as he passed her tissues soaked in cold water from the sink and she fell into the water, he alleged.

Huntley denied he had planned or expected the fall or deliberately pushed the schoolgirl, and said the next thing he heard was a splash followed by Jessica screaming: "You pushed her, you pushed her."

He said: "When Holly fell into the bath, I was stood there waiting for some movement or for her to get up . . . there was no movement, I just panicked and froze."

He added: "I couldn't think. Stood here, it's logical just to pull somebody out of the bath, especially when they are not moving. I could not think."

Huntley said "panic and screaming" had stopped him thinking clearly, and that his next memory was of putting a hand over Jessica's mouth to silence her screams, and might have put another hand out to "restrain" her.

He added: "At some point it hit me what I should be doing - to get Holly out of the bath."

Huntley let go of Jessica and he said: "She fell to the floor.

"To be honest, it didn't really register that much. My main priority now was to get Holly out of the bath."

Huntley described how he pulled Holly out of the bath and laid her on the floor before checking her wrist and neck for a pulse, but found none.

Stephen Coward, his QC, asked: "What about Jessica?"

She also showed no sign of life and Mr Coward asked what was his next memory.

"Sat in the corner on the landing, just looking at Jessica," he said, adding that he had no memory of getting there.

Huntley told the jury: "I had been sick."

He had no idea how long he was huddled there and admitted he made no attempt to resuscitate the girls.

Asked if he would do anything differently now, he said: "If I had pulled Holly out of the bath and got her to regain consciousness, everything would have been OK."

Huntley said he had decided not to call the police, a decision which he said he regretted by the next morning.

"I was thinking of calling the police but I didn't believe what had happened," he said.

"I kept thinking 'How do I explain this to the police?'.

"If you can't believe what has happened yourself, how are you going to expect the police to believe it either?"

Instead, he bundled their bodies into the boot of his Ford Fiesta.

He repeatedly insisted that he had no plan at that stage, but just knew he needed to get them out of his house, adding: "I was just driving. I did not have a destination in mind."

Huntley said he drove to Lakenheath, near where his father used to live, saw tracks leading off the Wangford Road and decided to drive down them.

He decided to dump the bodies into the first gap in vegetation that he found, without realising that a 6ft deep ditch ran alongside the track.

He said: "I went to the boot of the car and opened the boot and picked up one of the girls - I'm not sure which one.

"The bank of the ditch was too steep for me to carry the girls down so I had to place her ... at the top of the ditch so she rolled down.

"I then returned to the car and did the same."

He described how he cut the girls' clothes off their bodies, in case there were carpet fibres from his car or house on them, but denied that he ever touched the girls sexually.

He then doused the bodies with petrol, set fire to them and "drove away as quickly as I could".

Huntley denied ever having gone back to the bodies. He burned the girls' clothes when he got back to the college.

He denies the double murder but has admitted conspiring to pervert the course of justice. His then girlfriend Maxine Carr, 26, a former teaching assistant at the girls' primary school, denies the conspiracy charge and two counts of assisting an offender.

Huntley said he had tried to tell Carr what had happened "but I couldn't get the words out".He told her the same version of events that he gave others at the time.

Huntley said she volunteered to say she was in Soham, and not in Grimsby, on August 4, after he told her he believed he would be arrested.

He told the court how he was falsely accused of rape in 1998, and the case was later dropped by the Crown Prosecution Service.

Mr Coward asked: "Did you intend to kill Holly and Jessica?"

Huntley said: "No, I didn't."

Mr Coward asked: "Did you intend to cause them really serious bodily harm?"

Huntley replied: "No, I didn't."

The case continues.