By Andrew Osborn
LONDON (Reuters) - Prime Minister David Cameron convened a meeting of his government's emergency response committee to discuss what more it could do to tackle a spike in attempts by migrant to enter Britain illegally via the Channel Tunnel from France.
Cameron is under growing pressure to deter the migrants, many of whom have traveled from Africa and the Middle East, after repeated disruption to cross-Channel passenger and freight traffic, which has become front page news.
Cameron will chair the meeting of the committee, known as Cobra, later on Friday after calls from some politicians to mobilize the British army to reinforce border controls.
The government has said it is working to erect new security fencing around the French port of Calais, the flashpoint for the crisis.
Re-elected in May, Cameron has promised to cut net annual migration to Britain to the tens of thousands, a pledge he failed to keep during his first 2010-15 term in office when it hit a near record high of over 300,000 people per year.
The issue is a sensitive one for Cameron as it plays into Britain's debate about Europe ahead of an EU membership referendum which he has promised to hold by the end of 2017 after trying to reshape his country's ties with the bloc.
Migrants have long gathered in Calais to try to board lorries and ferries to Britain. But Eurotunnel, the firm that runs freight and passenger shuttles via the Channel Tunnel, says their numbers have now swelled to around 5,000 people from about 600 and that it is struggling to cope.
It says the migrants have also become better organized, mounting nightly attempts in large groups to storm the facilities.
Eurotunnel has sometimes been forced to suspend its services because of such activity, causing disruption at what is one of the busiest times of the year for British holidaymakers.
The situation has caught the imagination of Britain's tabloid newspapers, becoming a political headache for Cameron, who has spent the past week in southeast Asia on a trade mission while the crisis has flared.
He is under pressure to get tough on the migrants from many lawmakers in his ruling Conservative Party who say voters are fed up with what they see as lax border controls.
But he also has to contend with political rivals unhappy with the tone of the debate. The opposition Labor Party has criticized Cameron for referring to the migrants as a "swarm of people." It said the term was dehumanizing and stirred public hostility against people often fleeing poverty and conflict.
(Editing by William Schomberg)