Theresa May has insisted new security measures are starting to take effect at Calais - but admitted the migrant crisis could shift to other European ports.
The Home Secretary disclosed that talks have begun with authorities in the Netherlands and Belgium as she toured a £7 million ring of steel surrounding the Eurotunnel terminal at Coquelles.
Carrying out the first visit by a minister to Calais since the emergency escalated, Mrs May is signing a new agreement with her French counterpart Bernard Cazeneuve.
It includes an unprecedented deployment of British police to work in a joint "command and control" centre to target trafficking gangs.
Mrs May disclosed that Britain has begun with Belgium and Holland amid suggestions that traffickers may attempt to smuggle migrants to the UK through different ports after security was strengthened at Calais.
Immigration Minister James Brokenshire has spoken to officials in the two countries and is expected to travel for further discussions.
Mrs May also said other northern French ports such as Dunkirk are being scrutinised.
The Home Secretary said: "We are also looking at the security of other ports. We are very well aware of the possibility of displacement.
"The Immigration Minister has already had discussions with the Dutch and Belgian authorities to look at ports there and whether work might need to be done there. Of course we are looking at other ports like Dunkirk."
Zeebrugge in Belgium and the Hook of Holland are seen as potentially vulnerable.
Mrs May said the governments of both countries have been working together with an "excellent level of collaboration" and claimed measures announced in recent weeks have had an effect.
She said: "We have already taken a number of steps that have started to improve the situation here in terms of numbers of people trying to access the tunnel and get through to the UK. But the work must continue."
Both countries working together
She said the problems seen in Calais start elsewhere in the world.
"Migrants are trying to come to Europe with organised gangs, people smugglers, trafficking people through to Europe. What we see here is a symptom of a wider problem."
Those trying to reach Europe include some refugees and "many, many economic migrants," the minister said.
She said law enforcement agencies of both countries are working together to deal with trafficking gangs.
Mrs May added that many migrants are making a "dangerous" journey.
"They risk their lives, many of them having paid people smugglers money to try to get them here to Calais and to the UK.
"We must break these criminal gangs. We must break the link between leaving Africa and other parts of the world."
Mrs May visited Coquelles, where a 2km stretch of four metre high barbed wire fencing has been erected at the freight and vehicle terminal, which has been a hotspot for migrant incursions.
The barrier will be extended by a further 1.5km on each side to reach the mouth of the tunnel.
A Border Force official said the measures aimed to "incarcerate" 14 platforms at the site.
Disrupting organised criminals
The Home Office said the new police command was aimed at disrupting organised criminals who attempt to smuggle migrants illegally into Northern France and across the Channel by ensuring intelligence and enforcement work is more collaborative.
The work of the police contingent will be led by two senior "gold" commanders - one from each country.
They will report regularly to the Home Secretary and her French opposite on the extent of immigration-related criminal activity on both sides of the Channel.
Up to 5,000 migrants are estimated to be in Calais and a number have died attempting to cross to Britain.
The crisis appears to have abated since its peak earlier in the summer. Eurotunnel said earlier this week that the number of migrants trying to get into the terminal has fallen to around 150 a night, down from a high of 2,000 at the end of July.
There were claims today that the UK's tough stance could be undermined by French plans to offer hundreds more beds to those massing in Calais.
Paris wants £1.7 million in EU funds to accommodate around 500 more migrants, the Daily Mail reported.