The Armed Forces Minister has apologised after a coroner criticised the “systemic failures” which caused an explosion on board a nuclear submarine, killing Black Country sailor Paul McCann.

Bob Ainsworth admitted “avoidable failings” brought about the blast on HMS Tireless in March 2007. His comments came after a seven-week inquest on Leading Operator Mechanic Paul McCann, aged 32, from Halesowen, and Operator Mechanic Anthony Huntrod, 20.

The two died while on a mission under the arctic ice.

The explosion in a confined compartment was caused by a damaged Self Contained Oxygen Generator (Scog) moments after it was activated by one of the men.

The Scog, a 1.5kg flask, contained a chemical briquette which would normally release oxygen when fired but could burn with “ferocious violence” if contamination or damage had occurred, the inquest heard.

It was also revealed during the inquest that the Scog in question could have been retrieved from a waste dump.

Sunderland coroner Derek Winter criticised the Ministry of Defence’s handling of Scogs in his narrative verdict, given yesterday.

The Sunderland inquest heard that almost 1,000 Scogs were recycled from a hazardous waste dump in Devonport and brought back into service by civil servant Christopher Clark, of the Marine Environment Survivability and Habitability project, as a cost-cutting measure.

Mr Winter said Scogs were not properly inspected, were left in the open air, roughly handled and badly stored on board and he criticised Mr Clark’s decision to reissue the Scogs from the dump.

He said: “Those systemic failures led to the contamination and damage, that in turn, caused the explosion.”

Armed Forces Minister Mr Ainsworth said: “I would like to unreservedly apologise to the families, as I have done previously in the House and in person, for the avoidable failings, for which this department is responsible, which brought about this tragic incident.”