Security will be ramped up at the Channel Tunnel after Britain and France agreed a new package of measures, according to reports.
The steps include 200 extra private security guards funded by the UK, French police reinforcements, additional fences provided by Britain and more CCTV.
Downing Street admitted the UK would fund "most if not all" of the new security measures in Calais, the Sunday newspapers are reporting.
It comes after David Cameron called French President Francois Hollande to discuss the migrant crisis.
The Prime Minister has warned the crisis, which has seen some 5,000 desperate migrants lay siege to the tunnel in the hope of reaching Britain, could last all summer.
Harriet Harman has written to Mr Cameron demanding he ask the French to compensate Britons affected by the chaos in Calais.
Labour's interim leader says the Prime Minister should be doing more to recoup the cost of the crisis to haulage companies, who have seen their vehicles stacked on the M20 in Kent due to disruption to ferry and Channel Tunnel services.
They are estimated to be losing €990,000 a day as a result of the delays.
"You have failed to initiate any diplomatic pressure on the French government to assess asylum claims and make sure proper immigration procedures are followed," Ms Harman told the PM.
"Instead you have chosen to inflame the situation with incendiary and divisive language, which will serve only to escalate the problem."
A Downing Street spokesman responded: "As the PM has said, playing a blame game is not going to offer a solution for anyone.
“What we are focused on is working closely with the French authorities and taking action to both boost security and reduce disruption for hauliers and businesses. We welcome the French police reinforcements, which have helped to strengthen security at Eurotunnel.
"We are already pursuing a comprehensive approach to tackling illegal migration into Europe; supporting rescue operations in the Med, disrupting trafficking gangs and working to stabilise the migrants' home countries."
The Government is considering using car parking space at Ebbsfleet railway station, or the disused Marston airport, to ease lorry stacking on the M20.
The motorway was reopened for normal traffic on Saturday evening.
