The Home Secretary today extended her ban against marches in the capital after a request from police chiefs.
Theresa May outlawed marches in the City of London area after banning similar demonstrations in nearby Tower Hamlets, Newham, Waltham Forest, Islington and Hackney.
The decisions came amid fears of violence and disorder if a planned march by the English Defence League next month went ahead.
Police made the request for a supplementary ban amid particular concern surrounding the EDL's plans, it is understood.
Assistant Commissioner Frank Armstrong, of City of London Police, said: "This is not a decision we take lightly, but is, we believe, an appropriate response to prevent a displaced march or demonstration resulting in serious public disorder within the City of London.
"We are, as ever, working closely with the Metropolitan Police around public order events and will continue to keep the City safe."
A Home Office spokesman said: "The Home Secretary has today given her consent to a ban on all marches in the City of London for a 30-day period.
"This supplements the Banning Order in place for Tower Hamlets and four neighbouring boroughs. The decision has been taken following consideration of the legal tests in the Public Order Act."