Ian Huntley reacted angrily in court when he was accused of deliberately drowning Holly Wells in his bathroom.
Holly Wells and Jessica Chapman were best friends
Richard Latham, QC, prosecuting said: "The only way that child could have
drowned in that bath is if you were holding her under water."
But Mr Huntley, who denies murdering 10-year-old Holly and her best friend Jessica Chapman in Soham said: "I was not holding her."
He claims Holly died accidentally after falling into his bath last August.
However, he admitted he had killed Jessica by putting his hand over her mouth to stop her screaming and had told 'barefaced lies' to police to cover his tracks.
"I didn't deliberately intend to kill her," he told the Old Bailey.
In a heated exchange Mr Latham asked the defendant: "Jessica was screaming because you were murdering Holly, that's
the truth isn't it?"
Mr Huntley's voice, which had previously been calm throughout, began to rise as he denied this.
Mr Latham said: "You have just lost your temper with me, haven't you?"
Mr Huntley replied: "Yes."
"Did you lose your temper with one of these girls on that Sunday
Mr Huntley replied: "I had no reason to lose my temper."
Mr Latham said: "Did you become the assertive individual you became two minutes
Mr Huntley said: "No I did not."
The ex-caretaker told the court that he put the bodies into his car before dumping them in a ditch near Lakenheath, Suffolk, cutting their clothing off and burning their bodies. He agreed it had been a "cold and ruthless" act.
Mr Huntley admits one charge of conspiring to pervert the course of justice and his former girlfriend Maxine Carr denies helping an offender and conspiring to pervert the course of justice.
Mr Latham said Mr Huntley's claim that he had invited Holly into his house to stem a nosebleed was "rubbish".
He repeatedly challenged the defendant's version of events on the day the girls disappeared from their homes in Soham, Cambridgeshire, on Sunday 4 August last year.
Mr Huntley admitted that by 8 August, he and Ms Carr had agreed they would lie about what happened, but said it was her idea.
He agreed that telling the police and the media that they had been together on the night the girls disappeared was a "bare-faced lie".
And he admitted the lie was to put the police off the scent and divert attention away from himself, but added: "I don't think Maxine thought of it in that way"
Ms Carr had actually been in Grimsby with her mother and the two spoke three times on the phone on the Monday evening.
Mr Latham said: "You were putting your heads together during that
He suggested Ms Carr had "put ideas" into Mr Huntley's head to clean the house thoroughly and check what the neighbours were telling the police.
Mr Latham said Mr Huntley had been changing his story even during the course of the trial, because "you were inventing a defence to fit the facts."
But Mr Huntley said his memory has been improving since the summer, following a period of memory loss caused by the trauma of the girls' deaths.
The former school caretaker admitted he acted "inexcusably" by approaching Holly's father, Kevin Wells, to wish him well in the search for his daughter when he knew she was dead.
But he denied "playing with the emotions" of the parents.
The barrister said he had been acting in a calculated and callous way throughout, after temptation arrived when the girls came to his door.
Mr Huntley denied luring the girls into his house by pretending Ms Carr, who was a classroom assistant at the girls' school, was at home.
But he admitted it was "inappropriate" to let Holly into his bedroom while Jessica used
He said he failed to react after Holly fell into the bath water because he was "frozen
by panic" and needed to "collect his thoughts".
The case continues.