According to a background paper from 2006, the Terrorism Act 2000 proscribes 40 international terrorist organisations. This number is in addition to 14 Northern Irish organisations still proscribed under previous legislation and under Schedule 2 of the Act. The list has been expanded since the initial proscription, with no organisations having been deproscribed as of that date.

More recent information or an exact current figure is not explicitly stated in the results, but it is confirmed that dozens of organisations are proscribed under the Terrorism Act 2000. The list is maintained by the Home Secretary and updated periodically.

Hence, the most precise historical figure is 40 international terrorist organisations proscribed under the Terrorism Act 2000, with the total number likely to be somewhat higher as of 2025. For the precise current number, consulting the latest official list from the UK Home Office would be necessary. Would an updated direct count or official current list from the government be preferred next?