London 2012: Sailing security threat from 'unnamed' vessels
Concerns have been raised that "unnamed" vessels could pose a security threat in Weymouth during the Olympics.
Ex harbour master Cdr Peter Tambling said too many boats which could not be identified passed through the area where the sailing events will be held.
The fears were raised as a large Olympic security exercise began off the Dorset coast.
The Navy said it was not concerned about whether boats had names or not.
A spokesman said it planned to maintain a plot of all vessels in the area and would intercept them if necessary.
Exercise Olympic Guardian, in Weymouth Bay and Portland Harbour, involves the Royal Navy and Dorset Police.
'Jet-ski off radar'
Navy flagship HMS Bulwark and other ships have been stationed off Dorset.
Cdr Tambling said: "What really worries me is the number of boats navigating with no names on or ID marks.
"How do you control a terrorist situation when you've got to battle with that? Half the yachts have no marks on them.
"We are the only country in Europe where boats are allowed to go to sea with no name on the bow.
"To my mind if there's going to be any threat it will be on a jet-ski which won't show up on radar."
Royal Navy Commander Mark Southorn said: "The whole purpose of having HMS Bulwark off Weymouth is to maintain a 'recognised maritime picture', using a combination of radars and other sources.
"It doesn't matter what the names of the vessels are so long as we have a complete picture.
"We would react if the vessel does something unexpected. We would try to communicate with it and, as a last resort, send an RIB over to intercept."
Further land and air exercises involving RAF helicopters and jets will take place in the London area until 10 May.