Britain and France have combined to call for international efforts to address "a global migration crisis" which has seen thousands of people trying to force their way into the Channel Tunnel in an effort to reach the UK.
French riot police sprayed migrants with chemical irritants after they tore down security fences at the Eurotunnel terminal in Calais on Saturday night.
Downing Street announced that the UK will fund additional private security guards, fencing and CCTV cameras to improve security at the terminal, while more French police are to be deployed to the border over the summer.
And a consultation has been launched on stripping financial support from the families of migrants who fail in their applications for asylum.
Meanwhile, there was controversy over the cost to taxpayers of housing migrants who have arrived through the Tunnel, after contractors Serco confirmed that around 100 were being accommodated in hotels in the North West as increased numbers outstripped available places in the community. The Home Office said that the use of hotels was "only ever acceptable as a short-term contingency measure".
In a joint article for the Sunday Telegraph and French newspaper Journal du Dimanche, Home Secretary Theresa May and her French counterpart Bernard Cazeneuve called on other EU nations to take action to address the root causes of the chaos in Calais.
They said that solving the crisis was "the top priority" for both governments, but added: "What we are currently facing is a global migration crisis. This situation cannot be seen as an issue just for our two countries.
"It is a priority at both a European and international level. Many of those in Calais and attempting to cross the Channel have made their way there through Italy, Greece or other countries. That is why we are pushing other member states, and the whole of the EU, to address this problem at root."
A long-term solution to the problem must involve persuading would-be migrants hoping for a better life in Europe that "our streets are not paved with gold", they said.
Liberal Democrat leader Tim Farron urged David Cameron to reconsider Britain's refusal to take part in a European Commission scheme to relocate those arriving in Italy and Greece by boat.
In a letter to the Prime Minister, Mr Farron said: "Calais is the tip of a humanitarian crisis and while I and the Liberal Democrats support your action protecting our borders, I call on you to ensure that the UK acts in solidarity with the EU in providing asylum for those fleeing persecution and war."
He added: "Opting in to the Commission's proposal would ensure that the UK plays our full part in helping to deal with the immediate crisis in the Mediterranean and offer our protection to some of the most vulnerable refugees. The collective failure of EU member states to deal with this crisis has led to immeasurable suffering and contributed to the devastating situation we now see at Calais."
Setting out new security measures agreed following a phone conversation on Friday between Mr Cameron and President Francois Hollande, a Downing Street spokesman said: "The Prime Minister is clear he wants to see more security and tougher action at the border, which is what the measures agreed with France overnight are all about."
Although the M20 motorway was reopened for normal traffic late on Saturday, after weeks in which parts of the coastbound carriageway have been used as a parking lot for lorries unable to cross the Channel, Number 10 confirmed that efforts continue to secure additional parking zones in Kent to reduce the impact on local residents and businesses.
Labour has called on the Government to demand compensation from Paris for truckers, businesses an holidaymakers hit by the disruption, citing Freight Transport Association estimates that the crisis has cost hauliers £700,000 a day. But Downing Street said the PM had made clear he would not "play the blame game".
Scotland's First Minister Nicola Sturgeon said the economic impact of the crisis was "disproportionately severe in Scotland" costing seafood firms millions of pounds a week and placing future orders in jeopardy.
But she stressed: "Our primary concern over the current situation in Calais must be to play our part in addressing the underlying humanitarian issues. Increasing security at the Channel Tunnel, whilst welcome, will only help in the short term, and is not addressing the root cause of the issue."
Responding to Ms Sturgeon's letter, a Downing Street spokesman said: "We understand the problems faced by exporters and hauliers and are determined to do everything we can to bring the disruption to an end ... We know the disruption is a particular problem for perishable goods and the Department for Transport is already working with hauliers and transporters to ensure these goods are prioritised.
"On the issue of relocation, the UK has long played a leading role in resettling the most vulnerable people and providing refuge in the UK. But our position on EU-wide resettlement schemes is clear, resettlement schemes are best run at a national level and we will continue to resettle the most vulnerable people under our existing schemes."