To report an imminent threat call 999 or ring the Anti-Terrorist Hotline on 0800 789 321
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Government departments

MI5 works particularly closely with the Home Office and has strong links with the Foreign & Commonwealth Office, the Cabinet Office, the Northern Ireland Office, the Department for Business, Innovation and Skills, and the Ministry of Defence. We also advise all central government departments and agencies on protective security matters.

Other intelligence agencies

We work very closely with both the Secret Intelligence Service (SIS) and the Government Communications Headquarters (GCHQ). We each have different but related functions, and there are many areas where we provide mutual assistance. We promote co-operation when a result can be achieved more effectively with the help of one or both of the other agencies. We are also a major customer for any intelligence they produce which is relevant to our functions and supplements our own collection efforts.

A police car

We work closely with the police

Law enforcement agencies and the armed services

In addition, we have a close partnership with the police in Great Britain and Northern Ireland, predominantly through the national counter terrorist police network, Metropolitan Police, Police Service of Northern Ireland (PSNI), Police Scotland, and local force Special Branches. We also work with other national law enforcement agencies including the National Crime Agency and Border Force. We receive help from the police and our other law enforcement agency partners in many areas of our work, provide them with information and intelligence assessments on current threats, and collaborate closely with them on investigations that may result in criminal proceedings. We have also provided unique support to the police and other law enforcement agencies in the field of serious crime, although this work is currently suspended due to other operational priorities.

MI5 took lead responsibility for Northern Ireland's national security intelligence work during 2007, bringing Northern Ireland arrangements into line with the rest of the UK. We work in close partnership with the PSNI, who continue to provide the operational police response in countering terrorism and protecting the whole population of Northern Ireland.

Foreign security and intelligence services

We are charged with protecting national security, which may be threatened both in the UK and overseas. We work closely with our counterparts in other countries to ensure the security of UK interests overseas. In an increasingly globalised world, threats to our key partners have an impact on the UK's national security too. In many areas of our work we rely heavily on the support of SIS and the assistance given by foreign security and intelligence services.

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