Ismael Abdurahman, 23, was charged under anti-terrorism laws on Wednesday and was due to appear before a magistrates court in London on Thursday, Scotland Yard said.
The man is not one of the four key suspects whose pictures were released after the abortive bombings. They are accused of carrying out the operation. Their bombs apparently failed to explode properly.
"Between 23 July and 28 July he had information he knew or
believed may be of material assistance in securing the apprehension, prosecution or conviction of another person in the UK for an offence involving the commission, preparation or instigation of an act of terrorism," the charge against Abdurahman read.
Scotland Yard said the suspect, who lived in south London, was first arrested on 28 July under the Police and Criminal Evidence Act (Pace) on suspicion of harbouring an offender.
"He had information he knew or believed may be of material assistance in securing the apprehension, prosecution or conviction of another person in the UK for an offence involving the commission, preparation or instigation of an act of terrorism"
Charge against Ismael Abdurahman
The following day, he was re-arrested under the Terrorism Act.
The police also confirmed that a man who was detained over the weekend in Brighton, on the south coast, had now been released with no further action.
British authorities are holding a total of 15 people in custody in relation to the attacks, while one of the prime suspected would-be bombers, Hamdi Issac, is being detained in Rome.
An Italian judge, meanwhile, said Britain had delivered the documents he needed to start extradition proceedings against Issac, a 27-year-old Briton born in Ethiopia who is also known as Osman Hussein.
Judge Domenico Miceli, in charge of the case, said a date for a
hearing could be established this week and that the hearing itself might take place this month.
Issac was formally charged in Italy on Monday with international terrorism and with possessing false identity documents.
Britain considers Issac as one of four prime suspects in the
botched attempts to bomb three Underground railway trains and a double-decker bus.
The other three are among those in custody in London.
UK officials are trying to extradite
Osman Hussein from Italy
In a fast-moving, international investigation, Zambia officially
announced it would deport Haroon Aswat, the alleged mastermind behind London's first attacks on 7 July, who was arrested in the capital Lusaka two weeks ago.
"We had discussions with the governments of the US and Britain and finally agreed that Mr Aswat should be deported to his country which is Britain," Zambian President Levy Mwanawasa said in Lusaka, adding that the deportation "will be soon".
Aswat, 31, has been named in US and British media reports as the suspected ringleader behind the bombings.
Increasing hate crimes
The developments come as a senior member of London's Metropolitan Police warned of a sharp upturn in reported hate incidents directed at Muslims, and said it could hamper the ongoing investigation.
Since 7 July, according to police figures, crimes motivated by religious hatred have soared by almost 600% in the British
capital, home to seven million people.
There were 269 such incidents reported since the first blasts,
compared to 40 over the same three-and-a-half week period in 2004 - mostly minor assaults or low-level abuse, but also including attempts to attack mosques.
In the United States on Wednesday, a briefing given by the New York Police Department to city business leaders revealed that the London bombers cooked up their explosives using mundane items like hair bleach.
They stored them in a fancy commercial refrigerator that was out of place in their dingy flat, and cell phones were likely used to set them off.
"Initially it was thought that perhaps the materials were high-end military explosives that were smuggled, but it turns out not to be the case. It's more like these terrorists went to a hardware store or some beauty supply store"
The briefing - based partly on information obtained by NYPD detectives who were dispatched to London to observe the investigation - was part of a programme designed to encourage more vigilance by private security at large hotels, Wall Street firms, storage facilities and other companies.
NYPD Commissioner Raymond Kelly warned that the
materials and methods used in the London attack were easily
adaptable to New York.
"Initially it was thought that perhaps the materials were high-end military explosives that were smuggled, but it turns out not to be the case," Kelly said. "It's more like these terrorists went to a hardware store or some beauty supply store."
The NYPD officials said investigators believe the bombers
used a peroxide-based explosive called HMDT, or
hexamethylene triperoxide diamine, which can be made using
ordinary ingredients such as hydrogen peroxide (hair bleach),
citric acid (a common food preservative) and heat tablets
(sometimes used by the military for cooking).
Among other details cited by Michael Sheehan, NYPD deputy commissioner of counter-terrorism, were that the bombers transported the explosives in beverage coolers tucked in the backs of two cars to the outskirts of London and the three bombs that exploded in the underground railway were believed to be detonated by cell phones that had alarms set to 8.50am.