The Government has said it has no idea how many terrorists may have been deported back to the UK.

Immigration Minister Caroline Nokes made the admission in a response to a parliamentary question lodged by Independent MP John Woodcock in January.

Mr Woodcock asked the Home Office for the number of UK nationals who have been deported 'on suspicion of terror offences' by country of deportation in each of the last five years.

Some 850 Britons are believed to have joined ISIS in Syria or Iraq. Intelligence officers believe half of those suspected terrorists have returned to the UK

Immigration minister Caroline Nokes, pictured, admitted data on UK citizens deported back to Britain is not recorded as Britons are not subject to immigration controls on arrival

Following a delay of almost five months, Ms Nokes responded: 'The UK government does not hold a complete data set relating to individuals deported to the UK, broken down in this way, since UK nationals are not as a matter of course subject to immigration controls on arrival.

'In addition, not all countries will disclose that they are deporting an individual to the UK or that that there is a terrorism concern relating to them.

'The UK has developed close partnerships with countries which are a priority for joint work on international counter-terrorism in order to manage the risk to the UK from terrorism.

'Data on the use of tools and powers available to manage the threat to the UK from individuals suspected of involvement in terrorism, including managing their return to the UK, are due for publication shortly in the annual Government Transparency Report on Disruptive and Investigatory Powers.'

An estimated 850 Britons travelled to Syria and Iraq in order to join ISIS. Approximately half of these people are believed to have returned to the UK.

Chairman of the Intelligence and Security Committee in the House of Commons Dominic Grieve told The Express: 'There is quite a high level of co-operation between countries.

'The EU is a great facilitator of this, and there’s co-operation with lots of other countries which leads to them telling us they have arrested a British national and are sending them back.

'But the co-operation needs to be improved as much as possible. There are some countries, usually those with very poor human rights records, where communication is very difficult.'