David Cameron will warn today that Britain faces a growing security threat from Somali-born youngsters who have been "poisoned by radicalism", as he calls for a fresh drive to rescue the east African state from the grip of terrorists and pirates.
The Prime Minister will host an international conference this week on Somalia, which will be attended by representatives of more than 50 governments and international organisations, including the US Secretary of State Hillary Clinton and the UN secretary general Ban Ki-moon.
Mr Cameron will meet Somali community leaders in this country today to appeal for their help in the fight against terrorism here and in the struggle to bring stability and peace to their trouble-torn homeland.
Up to 50 Britons are believed to be fighting for al-Shabaab, the militant group linked to al-Qa'ida which controls much of the centre and south of Somalia. Intelligence sources fear that they could return with the expertise to launch terror attacks in the UK.
Speaking ahead of today's meeting, Mr Cameron said it was in both Britain's and Somalia's interests to bear down on terrorism and to create a political settlement in their homeland. He dismissed suggestions that Somalia's problems were simply too difficult to tackle.
"The threat to our national security is growing. Young British minds are being poisoned by radicalism," he said. "The problems in Somalia can only ultimately be solved by the people of Somalia. But our national interest is clear: we can't just let all this carry on."
Mr Cameron said: "There are many Somalis who have made their home in this country. We can't build peace without them. My message is this: Don't go back and fight. Help your homeland by doing all you can to back the political process and to build the rule of law."
Somalia has been ripped apart by civil war for the past 20 years, with the central government now only able to exert its control over small parts of the country. Ethiopian and Kenyan troops have intervened to prevent Islamist-inspired violence crossing the border.
As the rival military groups have fought each other for supremacy, the country has been hit by a massive humanitarian crisis, with up to 100,000 people starving to death last year. The power vacuum has also allowed groups of Somalian pirates to disrupt international trade as they roam off the east African coast.
However, Britain believes that there are now a few glimmers of light showing following a political agreement this weekend among Somali leaders. Key Somali leaders have signed a plan to try to end the country's two-decade-long political crisis. Britain will hope to build on that agreement on Thursday at the London conference, although no invitation has been issued to al-Shabaab.
William Hague, the Foreign Secretary, said that there was now "a moment of opportunity because things have improved a little in Somalia". Mr Hague suggested that the conference could agree to strengthen the political process in Somalia, boost the strength of African Union forces and agree on ways of combating the problems of terrorism and piracy.