The mission, called "Atalanta," is to last one year and will also be the first time that Great Britain has led an EU defence engagement. Rear Admiral Phillip Jones is to command the contingent, which will be headquartered in Northwood, Hertfordshire in the UK.

At a meeting in Brussels on Monday, the 27 EU foreign ministers are expected to approve rules of engagement that will authorise the use of military force in case of an attack.

Three NATO and Russian vessels and up to 15 other warships from a multinational force were already patrolling and escorting ships, along with a number of US Navy ships.

But NATO and the US Navy said they could not be everywhere, and American officials were urging ships to hire private security.

Portuguese Socialist MEP Ana Maria Gomes, vice chairwoman of the European Parliament's security and defence subcommittee, has repeatedly warned that the EU mission's deterrent effect would not be successful in the long run without tackling the root problem - state failure and poverty in Somalia.

Her calls were echoed by vice admiral Gerard Vallin, who heads France's naval forces in the Indian Ocean.

Mr Vallin told AFP: "Everything needs to be done to change Somalia from a failed to state to a country where the authorities are in a position to maintain law and order."

The EU fleet also faces the problem of strong support for the pirates amongst coastal communities who hail them as heroes, defending Somali fishermen against poachers from foreign nations, including Spain and France.

"The presence of European war ships will undermine the Somalis' ability to protect their natural resources from illegal fishing," said Mohamed Said, a pirate leader whose group has held the Saudi super-tanker Sirius Star for ransom since 15 November.

"Many of the polluters of Somalia's waters, those who dump toxic waste, are Europeans. This force will contribute to giving them unimpeded access to our waters," he told AFP.

According to UNOSAT, a UN-affiliated agency that analyses satellite data, the recent increase in naval vessels has done little to deter pirates, only forcing them to concentrate their attacks in specific areas.

"You would need at least 100 naval ships in the area to make a decisive impact, but this is impossible," Jean Duval, a maritime expert with French private maritime security outfit Secopex told the French news agency.