One of the 21 July bomb plot suspects was encouraged to lie by one of his co-defendants, a court has heard.
Manfo Asiedu is accused of involvement in the 21 July plot
Manfo Asiedu told Woolwich Crown Court that co-accused Muktar Said Ibrahim said he could lie during the trial because it was not an Islamic court.
But Mr Asiedu, 34, said he chose to ignore Mr Ibrahim's alleged advice because it was "not proper" to do so.
Six men deny conspiracy to murder and to cause explosions across London's transport network on 21 July 2005.
During his fourth day of giving evidence, Mr Asiedu told the jury he had decided he was "not going to swear on the Koran and end up lying".
"Morally, it's not proper for you to," he said. "When I said this, [Muktar Said] Ibrahim said I can swear and then I can say what I want to say because it's not an Islamic court."
After his defence barrister, Stephen Kamlish QC, asked him to clarify that Mr Ibrahim said he "shouldn't worry about lying having sworn on the Koran because it's not an Islamic court", Mr Asiedu said he had chosen to ignore the alleged advice.
"The decision was to speak the truth," he said.
Two months into the trial, Mr Asiedu had turned on Mr Ibrahim and accused him of planning an attack "bigger and better" than 7 July's attack on the London Underground.
He told the court Mr Ibrahim had encouraged him to go along with a false defence that the plan was only to set off fake bombs as part of a protest.
"I told Ibrahim that my legal team said if the hoax defence, it's not true, and I get in court and I swear on the oath and give false evidence, I will get caught out and be convicted straight away," Mr Asiedu said.
He told the court that Mr Ibrahim warned him not to "break ranks" and that his defence team was "just tempting" him.
Mr Asiedu reconstructed in court a sideboard "bomb" he claims he dismantled on 22 July.
Wearing gloves he used a plastic tub, sticky tape and string - instead of wire.
Mr Asiedu says that Mr Ibrahim booby-trapped a sideboard in the north London "bomb factory" to explode.
During cross-examination, George Carter-Stephenson QC, for Mr Ibrahim, questioned Mr Asiedu about his honesty.
He highlighted documents where he [Mr Asiedu] admitted he had previously used false names and dates of birth.
And on Friday he told the court that he had been cautioned by police after being found with cannabis, which he threw away and said it did not belong to him.
"Not all Muslims are perfect, not all humans are perfect," said Mr Asiedu.
The other men on trial with Mr Asiedu, of no fixed abode, and Mr Ibrahim, 29, of Stoke Newington, north London, are: Ramzi Mohammed, 25 and Yassin Omar, 26, of New Southgate, north London; Hussein Osman 28, also of no fixed address; and Adel Yahya, 24, of Tottenham, north London.
The prosecution have alleged the men set out to target London's transport network as part of an extremist Muslim plot but the devices failed to successfully detonate.
The trial was adjourned until Monday.