Pottengal Mukundan, director of the London-based International Maritime Bureau (IMB), said the threat remained despite warships patrolling the Somali coast and the Gulf of Aden -- the world's top piracy hotspot.
"I fear that hijackings will be higher this year compared to last year. This is based on the trend we are seeing so far," he told AFP.
"It is a very difficult challenge to defeat the pirates. They have moved (to operate in a wider area) to the north-east, east and south-east of Somalia," Mukundan said, adding that "we need more robust action."
Mukundan made the remarks after the latest incident Tuesday when pirates hijacked a Bulgarian chemical tanker in the Gulf of Aden with 15 Bulgarian crew members on board.
In 2009, there were 217 attacks by Somali pirates with 47 vessels hijacked and 867 crew members taken hostage. As a result, global figures rose to their highest in six years, with 406 reported incidents, up from 293 in 2008.
Somali pirates, armed with Kalashnikovs and rocket-propelled grenades, have now expanded from the Gulf of Aden into the open seas of the Indian Ocean, venturing as far as the Seychelles and beyond despite the presence of warships.
Alongside the European Union, the United States and other national navies have deployed warships off the Somali coast since December 2008 to protect shipping and secure maritime routes in the Gulf of Aden and the Indian Ocean.
Mukundan said the naval anti-piracy taskforce was unable to defeat the pirates because there was no law and order in Somalia, allowing piracy to flourish.
The ultimate answer to beat the pirates was "to have a responsible government in Somalia but we are very far from that," he said.
Mukundan said another powerful strategy against the pirates, who are venturing by as much as 1,000 nautical miles from the coast, is to destroy the vessels they use to launch speedboats and small skiffs to hijack vessels.
"The mother ships have to be taken out in order to disrupt the operations of the gangs involved," he said. "We would like to see the Indian navy intercepting and inspecting suspected mother ships."
Mukundan said Somali pirates were hurting maritime trade in the Indian Ocean by forcing vessels to take out expensive insurance policies. Some 25,000 ship sail through the Indian Ocean annually.
Despite the increased international military presence off Somalia's coastline -- the longest on the African continent -- pirates have raked in millions of dollars in ransom money.