Eighty-two of the 228 were charged. Security for the Olympics is thought to have contributed to the figures, while the Home Office highlighted arrests at a demo outside the US Embassy in 2011.
There were 22 arrests outside the embassy in Grosvenor Square, in central London, on 2 December last year, 20 of which were on suspicion of membership of banned group Muslims Against Crusades.
The proportion of terrorism-related arrests resulting in charges – 36% – is in line with the average rate for terrorism-related offences since the attacks on the US of 11 September 2001.
The figures, provided by the Association of Chief Police Officers (Acpo), also reveal that new measures allowing police to stop and search people for terrorist material have not been used since they were brought into force in March 2011.
The powers allow officers to stop and search people in certain areas, even when there is no direct suspicion of involvement in terrorism-related activity. The measures replaced more sweeping stop-and-search controls which the European Court of Human Rights ruled to be unlawful.
The figures also show that the use by the Metropolitan Police of stop-and-search powers where there is a suspicion of terrorist-related activity has fallen by just under half. In the 12 months to the end of the June, 679 people were searched by Met police using the powers, compared with 1,283 people in the previous 12 months. There were arrests after 5% of searches.