Theresa May has told the G7 summit British jihadis who go to Syria and Iraq to fight for Isil must be stopped and brought to justice in other countries before they can get back to the UK.

The Prime Minister wants G7 countries, including Britain, to share information and expertise with countries including Iraq so they can “prosecute any foreign fighters they capture”.

At least 800 British extremists have travelled to the Middle East to fight with Isil, and around half of them are thought to have returned, posing a huge terrorist threat on home soil.

Manchester suicide bomber Salman Abedi is among those known to have travelled abroad, where he may have received training in bomb-making before he detonated a device that killed 22 people earlier this week.

Mrs May is desperate to prevent jihadis returning to the UK, and proposed a series of steps to G7 leaders as she led talks on counter-terrorism at the summit in Sicily today.

Mrs May proposed:

:: Sharing the identities of foreign fighters who may pass through third countries on the way back to their countries of origin

:: Sharing expertise on policing, border security and watch-lists with transit countries

:: Providing training and resourcing to legal experts and police in Iraq and other countries to help them prosecute, extradite or deport foreign fighters

:: Sharing data on foreign fighters, such as names and nationalities, so they can be spotted as they cross borders.

:: Encouraging countries to pass on evidence such as videos or documents to the British authorities to help prosecute them if they make it back to Britain