Shipping giant Svitzer Marine admitted to a string of health and safety failures yesterday that helped contribute to 2007's deadly Flying Phantom disaster.

Three men were killed in 2007 when the fog-stricken Phantom capsized in a 40,000-ton carrier's wake and sank into the freezing River Clyde.

They were captain Stephen Humphreys, 33, from Greenock, deckhand Eric Blackley, 57, from Gourock and engineer Bob Cameron, 65, from Houston.

Their widows have campaigned ever since for the tug's owner Svitzer - a subsidiary of the multinational shipping firm Maersk - to be brought to justice.

But only yesterday did the case reach Glasgow's High Court, with the company pleading guilty to "failing to ensure, as far as reasonably practicable, the health, safety and welfare at work" of the crew.

Charges included the company's failure to overhaul its safety procedure after a similar incident in fog in 2000.

Andrew Henderson of the Thompsons legal firm representing the families said they welcomed the plea. But their grief had only been prolonged by an inquiry system that "systematically failed" them.

"While Svitzer's guilty plea will provide some comfort it remains to be seen what the High Court will deem a sufficient punishment," he added.

Peter Gray QC, acting for Svitzer, said the company was a "conscientious and reputable" employer that took pride in its prior safety record.

"Ever since December 19 2007, it has been a matter of the greatest regret that, in relation to the towing in restricted visibility, it failed to meet the very high standards it sets itself," he said.

Port operator Clydeport Operations Limited is also being prosecuted over the incident.

The Scottish Hazards Campaign's Ian Tasker greeted the news with relief, but agreed it would be little comfort for some.

But the company's directors did not face charges and the public prosecutor's office had still not decided whether to hold a fatal accident inquiry, he said.

"The employers plead guilty, they get a reduced sentence because they plead guilty - but families have been waiting six years for this. That's an unacceptable length of time," he said.

Unite Scottish secretary Pat Rafferty, whose union represents tug crews, called the inquiry system "little more than a lottery."

The news comes just a fortnight after MSPs criticised "outrageous" inquiry delays in a Holyrood debate, with Labour MSP Patricia Ferguson stumping up support for her bill to speed the process and make the judiciary's recommendations legally binding.