The International Maritime Organisation (IMO) has warned that many shipping companies are ignoring its recommendations on how to deter pirate attacks in the Indian Ocean and Gulf of Aden.
An "unacceptably high proportion" of shipping companies were failing to take recommended action, including having visible deterrent measures, the IMO said. They were also failing to heed navigational warnings in areas in which pirates were believed to be operating.
The group said all bodies connected with shipping, such as administrations, industry representatives, seafarer associations and shipowners must act in unison to deter pirates.
"Regrettably, there is disturbing evidence to show that, in too many cases, this advice has either not reached shipping companies or their ships, or has not been acted upon," it said. Pirate attacks have increased in the past 12 months, with 685 hostages currently being held for ransom across the Somali coastline.
Lt Cmdr Susie Thomson, a spokeswoman based in Bahrain for the UK Maritime Trade Operations, the primary liaison between naval and merchant shipping, said the extended reach of Somali pirates in recent months was dragging more crews within the range of kidnappers.
The majority of ships' crews have been "extremely responsive, because it's in their best interests at the end of the day to follow the guidelines", she said.
Some companies that do not regularly sail the Gulf of Aden and Indian Ocean said guidance on best practice for deterring would-be hijackers was welcome.
"We're happy to receive all these warnings and be aware of them in case that we get any business in that region," said Reza Sadeghi, the general manager at Atlantic Offshore Services, which supplies offshore services to the oil and gas sector.
Mr Sadeghi said that when planning for an expedition to tow a stricken vessel from the Indian Ocean to the Gulf, the company had found itself relying on the advice of external security firms.
He said information was often poorly communicated by the IMO to shipowners, despite the organisation having a registry of ship captains and contact details.
Gobind Kukreja, the general manager for shipping services at Gulf Agency Company, said adoption of the best management practices would take time.
"Nobody knowingly would ignore these," he said. "If you get hijacked, it's a big big problem … especially for the crew."
However, some companies said there were discrepancies between the advice given by insurers and the IMO.
Duncan McKelvie, the Dubai marine representative for the shipping company NYK Line, said: "The formal advice from the regulatory bodies concerned with shipping was not to take armed guards on board.
"But very many companies now have changed this and some insurance companies are giving an insurance break if guards - armed or unarmed - are carried onboard."
Nigel Booker, a former military intelligence officer and principal of Neptune Maritime Security, said whether international maritime bodies liked it or not, firing rounds into the ocean near approaching pirate ships deterred them from hijacking.
"Armed doesn't necessarily mean lethal force," Mr Booker said.
He gave the example of a contract his team had to protect a ship operated by a Scandinavian company that refused to have weapons on board.
During an attack last month, all pirates were repelled except for one, who doggedly tried to get aboard. He was badly injured by the electrified razor wire and ended up falling off the ship after being hit by a jet of water.
"Those are the results of non-lethal deterrents," Mr Booker said. "But he was cut to ribbons and there are lot of sharks in that area."