BRITAIN is considering sending more border security staff and sniffer dogs to Calais after David Cameron denounced the scenes showing scores of migrants trying to board UK-bound lorries as "totally unacceptable".

Services through the Eurotunnel were returning to normality after the day of mass disruption on Tuesday caused by striking French ferry workers. But the scale of the problem was underscored when local authorities revealed some 350 migrants were found in lorries heading for Britain in just a four-hour period.

At Prime Minister's Questions, Mr Cameron pointed out how the UK authorities were already working closely with their French counterparts, which included a £12 million investment. But, he stressed, that he was "happy for us to do more if that is necessary".

This, he explained, could include more security staff at Calais together with sniffer dogs. More fencing could also be erected around the rail tunnel entrances.

Commenting on the scenes of migrants seeking to break into UK-bound vehicles, the PM said they were "totally unacceptable scenes that we have all been witnessing in the last day".

Harriet Harman for Labour noted how British drivers were facing harassment and intimidation from the migrants at Calais, now said to number 3000, and asked what Mr Cameron was doing to "put pressure" on the French authorities.

But the PM said Britain's partnership with France on the migrant crisis was "strong", stressing: "There is no point either side trying to point the finger of blame at each other."

In a later Commons statement, Home Secretary Theresa May pointed out British and French authorities had, in the last two days, stopped "significant numbers" of migrants from entering the UK by climbing aboard lorries in the French port.

Today, Mr Cameron will discuss the specific issue of Calais with President Francois Hollande in the margins of the European Council in Brussels while the general migration crisis will be the main topic at the summit session this afternoon.

In a briefing, No 10 explained how there were two elements to the current crisis; dealing with migrants at Calais but also seeking to treat the root causes of the mass migration in the source countries in Africa, around the Mediterranean and beyond.

Mr Cameron's spokeswoman pointed out that the 3000 people rescued by HMS Bulwark in the Med came from 22 different countries. In the six months of this year alone, more than 100,000 migrants had reached the shores of Europe.

"Clearly, you need much more effort than just focusing on Calais and you need it further down the route and the chain, as it were...because this is a phenomenon affecting many countries across Europe and it's going to need a comprehensive and co-ordinated approach to it," she explained.

The spokeswoman said, on the intelligence front, that the UK Government would be establishing a 90-strong law rapid reaction enforcement team. It would consist of three hubs; one small deployment in Sicily, another in The Hague and the rest on standby in the UK to deploy as appropriate in Africa and around the Med to work with other countries to disrupt the criminal gangs.

Asked how long the PM envisaged this crisis would take to resolve, she replied: "We accept that this is a long-term challenge that we face. If you look at the numbers arriving across the Med last year and the signs are they will be similar numbers this year if not more; that's why we need a comprehensive approach that focuses on how you tackle the root causes of this and not just look at what happens to these migrants when they arrive in Europe."

Elsewhere, Ukip leader Nigel Farage said the UK had become "the number one destination of choice" for migrants due to the size of its employment black market and the failure to deport three-quarters of caught illegal immigrants.

"David Cameron's words today will not deter a single illegal immigrant from trying to break in to a car or a lorry," declared the MEP.