Manfo Asiedu, 34, of no fixed address, pleaded guilty earlier this month to conspiracy to cause explosions in connection with the failed attack.

He had been due to be re-tried at Kingston Crown Court when he changed his plea.

Earlier this year he stood trial alongside five others accused of plotting the attacks, but the jury was deadlocked in his case.

Four of the men were jailed for life in July at Woolwich Crown Court after being convicted of conspiracy to murder.

Muktar Said Ibrahim, Ramzi Mohammed, Yassin Omar and Hussain Osman were told they would serve a minimum of 40 years in prison.

Asiedu is likely to receive a lesser sentence because of his guilty plea.

Asiedu was supposed to be the fifth bomber but he "lost his nerve at the last moment", Woolwich Crown Court heard during the trial.

Instead, he dumped his bomb in a wooded area in Little Wormwood Scrubs, where it was found two days later.

The attacks on July 21 2005 took place on three Underground trains at Shepherd's Bush station, Oval station and Warren Street station, and a bus in Hackney Road.