What are the British and French governments doing to tackle the problem?
Home Secretary Theresa May has said that the UK Government will spend up to £7m on improving security around the entrance to the Eurotunnel.
She called for rapid installation of new security fencing and improved security at Coquelles to keep people out of the tunnel.
The UK is also working with the French to return migrants to their own countries and deal with criminal gangs who are profiting from them.
The French government said it would be reinforcing the means given to securing the border and the Eurotunnel site.
An extra 120 police staff, taking the number to more than 400, are being deployed in Calais in order to try to secure the perimeter.
But police say they remain outnumbered as there are thousands of migrants.
Will any government action be enough to stop migrants wanting to come to UK?
Groupe Eurotunnel, which manages and operates the Channel Tunnel, said the continuous pressure exerted every night requires a constructive and appropriate response from the governments.
French authorities have called on Britain to get what it calls the black market in employment sorted out. They say that, unlike in France and Italy, migrants can find work in the UK.