The format of future summits could change to limit rioting
Anti-globalisation campaigners laid siege to the Italian city during a weekend of rioting, which led to dozens of arrests.
One Italian demonstrator was shot dead by police and hundreds of people were injured during the uprisings, which have left the city with a multi-million pound clean-up bill.
G8 leaders have said that the format of future summits would be changed in a bid to limit disruption from rioters.
The mother of one of the British people arrested in Genoa believed her son had not been involved in the violence.
Armed guard
Janet Covell described her son Mark as a "timid man" and "a bit of a loner", but said he was not an aggressive person.
Mr Covell is under armed guard in hospital after suffering head injuries, broke ribs and internal bleeding, which required a blood transfusion.
The 33-year-old freelance web designer from Queen's Park in west London, was detained after a police swoop on the headquarters of the umbrella group co-ordinating peaceful protests, the Genoa Social Forum.
Retired bank clerk Mrs Covell from Burghfield Common near Reading, Berkshire, said: "Mark is not a rioting type person.
"He has his beliefs, but he wouldn't go out and cause violence.
"I received a phone call telling me he was in hospital. I was very surprised and I find it very distressing.
"I haven't been able to speak to him at all, but I'm told that he's quite down and that he just wants me to know that he's okay.
"I'd say he was liberal minded, but not what I'd call aggressive. He's a timid person really."
Arrest decisions
Mr Covell is said to be in a stable condition.
His mother said she was not aware that he had visited previous G8 conferences.
Police named other Britons arrested at the Genoa Social Forum headquarters as Nicola Doherty, 26, originally from Elgin, and Richard Moth, 32, who are both support workers for people with learning disabilities; Jonathan Blair, 38, from Newport; and Daniel MacQuillan, 35.
They remain in custody along with John Blair, 19, who was arrested earlier on Saturday and 25-year-old Lawrence Miles.
A spokesman at the British Embassy in Rome, said that under Italian law, those detained by police had not officially been arrested.
He said: "The investigating magistrates here have 48 hours to listen to the police and to say whether the arrest is confirmed.
"That is why we are not getting access to them yet."
A number of the Britons were not carrying any papers, the embassy spokesman said, leading to some uncertainty over their personal details.