Operators who sail with armed guards on board their ships to deter piracy increasingly fail to report any attacks, a development that "worries" the International Maritime Bureau (IMB).
"Vessels with armed private security do not report attacks attempts which other ships reported earlier," says Pottengal Mukundan, director of the International Maritime Bureau at a conference in London.
"There can be many reasons for this, but one could be that they fear being held accountable, or that the owners have clauses in their contracts preventing any reporting of attempted attacks by pirates", said Mukundan.
Mukundan also said at the conference that, until recently, far more alerts have been announced.
"But at the moment we have a feeling that such reports are being withheld. It is very important and essential that all pirate attacks are reported for the sake of the ships that come along after on the same path," said Mukundan.
During the third quarter of 2012 only a single attack on a merchant ship off the coast of Somalia has been registered, compared with 36 attacks in the same period last year.