The month-long Nautilus II, the second patrol mission held in the waters between Sicily, Malta and Libya under coordination of the EU's border control agency Frontex, paused last week due to lack of resources, according to the European Commission.

In a letter to Mr Frattini on 1 August, Mr Daul said: "I am sure that your intervention will have a decisive impact on the resumption of the Frontex mission in the Mediterranean area".

"It appears that the mission has been effective in reducing the number of arrivals to Malta, when one compares the number to the arrivals in the same period last month - 50% less," said Mr Daul.

"But if reductions in numbers were indeed due to the effectiveness of the mission, then it is clear that it does not make any sense at all to stop them in peak season, during the crucial summer months of August and September," he stated.

Last week, Maltese justice and home affairs minister Tonio Borg also called upon Frontex to relaunch its sea-border patrol mission.

"We of course hope that the Nautilus operation can resume as soon as possible," Mr Frattini's spokesman, Friso Roscam Abbing, told journalists in Brussels on Thursday (2 August).

"We have seen that the first phase of this operation has worked quite well…discouraging dangerous illegal clandestine immigration. So it is clear that it is an important element of our comprehensive immigration policy," he said.

Mr Abbing added that despite the very good start of the mission more needed to be done and he hoped EU member states which in February committed to support the mission with medical staff, ships, helicopters and other useful equipment for the sea-border controls, would fully live up to that commitment.

"We will do everything we can so that as of next year, the EU will have permanent missions in the high risk areas such as the Mediterranean and the Atlantic," he added.

Each year, around half a million illegal immigrants arrive in the EU.