Dover-bound migrants scale Calais security fence
Migrants in Calais have been filmed scaling a 5m high (16ft) security fence, giving them access to lorries already through customs.
The security breaches, occurring day and night, were filmed by the BBC.
Those who were caught were immediately released by the French authorities.
Home Affairs Select Committee chairman Keith Vaz said the French were not doing enough to address the problem, but the Mayor of Calais had previously said Britain should help more.
After watching BBC South East Today's footage, Mr Vaz said: "I'm astonished that the French authorities are not cooperating with us in preventing people putting their lives at risk on a daily basis in trying to get to the UK.
"This underlines the importance of working with the French government to try and deal with this severe problem."
There are an estimated 1,300 migrants in temporary camps Calais.
On Wednesday, scores of men tried to force their way on to a ferry bound for England, by running up the ramp.
They were prevented from accessing the vessel when staff raised the ramp and turned a fire-hose on them.
On Tuesday, the Mayor of Calais said she would blockade the port unless Britain helped to control the migrants.
Natacha Bouchart said that her city was being "taken hostage" by more than 1,000 migrants attempting to cross the English Channel from France.
Union representative Kevin Mills, who represents PCS members from the Home Office, said: "We are seeing breaches on a daily basis over there.
"The sad reality now is that it's in broad daylight and no-one seems to be doing much about it once they've got into that controlled area."
In March, migrants were filmed sitting on the axle's of lorries in a desperate attempt to cross the Channel.
A Border Force spokesman said: "We have already made improvements to security at Calais, working with the French authorities.
"We have, for instance, upgraded vehicle scanning equipment with the latest technology to detect people hiding in lorries and tankers and have increased the number of body detection dogs stationed at Calais."
A Home Offices spokesman said the UK government was providing a further £3m to help enhance port infrastructure in Calais and was awaiting agreement from the Calais Chambers of Commerce.
"We also continue to work with the French and other international partners to target the organised crime gangs behind smuggling and people trafficking, increasing joint intelligence work and co-ordination between law enforcement agencies.
"Action this year between the UK and France - together with police in Germany, Belgium and the Netherlands - has seen 20 organised gangs broken up and assets worth £1.4m (1.8m Euros) seized."