The tape also features a message from al-Qaeda number two, Ayman al-Zawahiri, as well as a reported separate reference to anti-terrorism raids in east London last month.
"What have you witnessed now is only the beginning of a string of attacks that will continue and become stronger," Shehzad Tanweer said in a northern English accent.
The 22-year-old and three accomplices killed 52 people and injured 700 more in attacks on three Underground trains and a double-decker bus last July 7.
The video, first broadcast by al-Jazeera, was shown on Britain's Sky News and the BBC.
The BBC, quoting unnamed intelligence sources, later said the video also contained a third person who referred to a high-profile raid on June 2 on a house in Forest Gate, east London.
Some media reports allege the third person is a young American Muslim convert, Adam Gadahn, also known as Azzam al-Amriki, believed to be in charge of al-Qaeda's propaganda unit.
The broadcaster said the revelation adds weight to the theory that the bombers were not just disaffected young British Muslims acting alone, but had direct help from al-Qaeda.
Tanweer and Khan visited Pakistan in 2004, according to the Pakistani authorities, while British Home Secretary John Reid has said that both were "likely" to have met Al-Qaeda figures during the trip.
In the video, Tanweer said attacks would continue unless Britain pulled its troops from Afghanistan and Iran, and financial and military aid to the US and Israel stopped.
He also referred to non-Muslims, and said they deserved to be attacked because they voted for a government which oppressed Muslims in the Middle East, Iraq, Afghanistan and Chechnya.
The footage includes pictures of people igniting explosives and armed with guns, as well as images of a man circling points on a map of London.
A similar video released in September featured fellow bomber Mohamed Sidique Khan.
Both bombers were dressed in headdresses, and the video bore the same logo reading "al-Sahab", which is believed to be a signature of al-Qaeda recordings.
The BBC said the video was likely to have been made in the Pakistani town of Quetta in the last five weeks.
Andy Hayman, Assistant Commissioner of London's Metropolitan Police, said the video's release must have been timed to cause maximum distress to victims' families.
"We are sure that the overwhelming majority of all communities are united in condemning any attempt to justify last year's terrorist attacks in London," he said.
British police earlier this week said they were investigating 70 cases at home and overseas,
Tanweer's family has refused to comment on the video, however a family friend said they would be devastated to see their son in the video.