Nigel Farage has warned that unless "something radical is done it is only a matter of time" before a British holidaymaker or lorry driver dies as a result of the Calais migrant crisis.
The UKIP leader told the BBC the French port was "virtually lawless".
He said he experienced it when migrants had tried to get into his car as he queued for the Channel Tunnel.
Home Secretary Theresa May said the government was "working very hard" to increase security.
She said "some people" had made it through the tunnel and would be dealt with in the normal way, adding that the crisis should be tackled "upstream".
Mrs May was speaking after holding a meeting of the emergency committee Cobra.
Labour's interim leader Harriet Harman called on the government to "get a grip" on the situation.
"This is not just a problem in Calais now, it's a major problem in Kent now as well," she said.
"As long ago as nine months ago we were pressing the government to get on to this and sort this out."
Labour MP Keith Vaz, who chairs the home affairs committee, urged David Cameron to hold talks with Francois Hollande on his return from Asia.
Mr Vaz said he had witnessed 148 migrants successfully make the journey illegally to England on Tuesday morning while at an immigration processing centre in Folkestone, Kent.
France says it will send extra police officers to Calais, and the Department for Transport announced it was relaxing rules that limit how long lorry drivers can drive for and how long they must rest.
Nine people have been killed at Calais in the last eight weeks.
The BBC's assistant political editor Norman Smith said the UK and France had reached an outline agreement on a scheme to repatriate some migrants - who are mainly from Ethiopia, Eritrea, Sudan and Afghanistan - but there were no details as yet of how it would work.
Mr Farage, who is an MEP for the south of England, said unless the French authorities were willing to "enforce law and order around those terminals", then the UK should step in.
British holidaymakers, businesses and residents in Kent were "paying a terrible price" for the failure of the French authorities and the shortcomings of the European Union's asylum policy, he told BBC London.
"I was stuck on that road outside Eurotunnel a few weeks ago. I was there for about 40 minutes and I was surrounded by scores of migrants, crossing the motorway and trying the passenger doors on my car. It is a pretty scary situation.
"The British government appears not to want to criticise the French government at all but frankly they are not doing enough."
Earlier, Mr Farage told LBC Radio that the army may be needed to be brought in to Calais - where the UK and France have juxtaposed border controls - to help a "very overburdened police force and border agency".
Politicians have called for freight to be diverted to other cross-channel routes to ease the pressure on the Dover-to-Calais crossing and to help address the problems on the M20 - where lorries have been "stacked" on a southbound stretch of the motorway for weeks, restricting access to non-freight traffic.
The Conservative MP for Folkestone and Hythe, Damian Collins, said the chaos at Calais was having "terrible" repercussions for Kent but the problems were happening "principally on French territory" and the French authorities needed to do more to defend the Channel Tunnel.
"They have allowed people to willingly break into the Channel Tunnel site," he told BBC Radio 4's Today. "I can't believe they would be that lax in protecting an airport or another sensitive facility but that has happened constantly throughout the summer. So they have to enforce their own restrictions."
Another Conservative MP, former minister Tim Loughton, pointed the finger at the French, who he said were "trying to make a European problem a British problem - if they can get it off their shores and on to ours, it's less of a problem".
The UK is providing £7m ($11m) of additional funding for new fencing at the terminal, the latest contribution it has made to try and secure the site.
Lib Dem leader Tim Farron said: "We are treating this as a security issue, but primarily it is a humanitarian one.
"We should be big enough to take a lead and accept our fair share of refugees... just moving in with force and building a bigger fence is not a solution."
Speaking in Malaysia on Wednesday, Mr Cameron said the situation in Calais was "very concerning" but the government was working closely with the French authorities and was prepared to contribute more money to improve security at the port.