It started with what should have been a routine voyage by the 740ft Panamanian bulk carrier, Red Jasmine, from Brazil to the UK to deliver animal feed.

It started with what should have been a routine voyage by the 740ft Panamanian bulk carrier, Red Jasmine, from Brazil to the UK to deliver animal feed.

But it ended with the Flying Phantom, one of three tugs tasked with assisting it through the Clyde, being dragged under with the loss of three of its four crew - skipper Stephen Humphreys, Eric Blackley and Robert Cameron.

Today, a damning report calls for a shake-up of safety procedures by the port operator, Clydeport, and the tug operator, Denmark-based Svitzer Marine.

The MAIB, describing port operator Clydeport's risk assessment as "immature" and "ineffective" said that it was "vital" that a comprehensive review of the port's risk assessment was conducted "urgently" by an independent marine expert. Clydeport also needed to appoint an appropriately qualified individual to scrutinise safety, it said.

Despite suffering a similar accident involving the Flying Phantom seven years previously, the report said there was "no defined operational limits or procedures" for the tug operators when assisting or towing in restricted visibility.

The Red Jasmine had been scheduled to arrive at 5am on December 15, 2007, but due to delays to other ships, it had been directed to anchor at Brodick Bay.

The MAIB report relates how, after four days of waiting, for which it had already accrued penalties for failing to deliver the cargo on time, the vessel finally set sail up the Clyde on Wednesday afternoon at high tide, following a "heated conversation" the night before between Clydeport officials, who were keen the voyage took place in daylight, and the agents. A compromise was reached, ensuring only the latter part of the passage, deemed less dangerous, took place after nightfall.

While fog had been forecast, the initial stage of the journey up the Clyde estuary took place in good weather conditions. It was only at 5.50pm, 10 minutes before the Flying Phantom capsized, that a report of heavy fog ahead, with visibility of 20 to 30 metres, was received.

Very soon, the conditions became treacherous. The MAIB report noted: "The fog was so thick that vehicles with their headlights on were used to highlight the edge of the berth." The skipper had been keeping the tow rope in line with Red Jasmine's foremast light, but still lost sight of it.

Without recourse to the normal means of piloting the vessel, the Flying Phantom's crew were left to conduct a form of "blind pilotage" for which they had received no training. "Even if they had been suitably trained, the Flying Phantom's bridge equipment was not well positioned to assist them," the report noted.

Very quickly, the pilot became lost. After the pilot requested Flying Phantom to pull the bow of the Red Jasmine to starboard, the tug started to heel over.

Amid these chaotic circumstances, the direct cause of the Flying Phantom's sinking was the failure of an emergency release mechanism to detach the tug's tow rope in time to stop it being dragged under by the Red Jasmine as it passed the smaller vessel, the report concluded.

Investigators said the emergency release system was "ineffective". It is thought likely that as a result of the significant load on the towing winch, the brake did not release quickly enough.

The speed of Flying Phantom's capsize would have been affected by the port engine room watertight door being left open, the MAIB said.

As well as this key technical failing, the MAIB report drew attention to a very similar accident that occurred in December 2000, when the Flying Phantom was acting as a bow tug assisting Abu Agila, a 10,000-tonne bulk carrier, which was bound for Shieldhall Riverside Quay.

After becoming disorientated in thick fog, as a result of poor visibility, the tug ran aground and was struck by the bow of Abu Agila, holing her below the waterline in the process.

Despite the subsequent review of the risk posed by fog on the Clyde, many of the recommendations were not followed up, and subsequent control measures were not implemented or were ineffective, the MAIB said.

There was a "lack of any procedures, training or limits for towage operations in restricted visibility", the report said. Although navigation in fog was covered in Svitzer Marine's safety management, there was nothing specific about assisting and towing in fog.

Fog had not been considered a particular problem by Clydeport's management because it caused the port to be closed on very few days each year, the MAIB said. It was considered that wind, a more common feature of the weather, kept the fog at bay.

The purchase of a £30,000 fog detection system was considered after the Abu Agila accident but, following inquiries, Clydeport did not buy it.

Better fog forecasting and detection systems were required, MAIB said, or "far more robust" procedures and contingency plans were needed to ensure ships can transit the river safely in fog.