Built in Yugoslavia in 1976, the unlucky vessel was abandoned in a Canadian harbour after its owners were embroiled in a debt scandal and failed to pay the crew.
The authorities in Newfoundland tried to sell the hull for scrap – valued at £600,000 – to the Dominican Republic, but cut their losses when it came loose in a storm on the way.
Sending the ship off into international waters, Transport Canada said it was satisfied the Lyubov Orlova “no longer poses a threat to the safety of [Canadian] offshore oil installations, their personnel or the marine environment”.
Experts say the ship, which is likely to still contain hundreds of rats that have been eating each other to survive, must still be out there somewhere because not all of its lifeboat emergency beacons have been set off.
Two signals were picked up on the 12 and 23 March last year, presumably from lifeboats which fell away and hit the water, showing the vessel had made it two-thirds of the way across the Atlantic and was heading east.
A week later, an unidentified object of about the right size was spotted on radar just off the coast of Scotland – but search planes never verified the find.
Pim de Rhoodes, a Belgian salvage hunter who is among a number looking for the Lyubov Orlova off the UK coastline, said: “She is floating around out there somewhere.
“There will be a lot of rats and they eat each other. If I get aboard I'll have to lace everywhere with poison.”
The head of the Irish coastguard, Chris Reynolds, said the ship was more likely than not to still pose a threat.
“There have been huge storms in recent months but it takes a lot to sink a vessel as big as that,” he said.
“We must stay vigilant.”