The families of a Watford solider and another UK serviceman killed in an incident of "friendly fire" in Afghanistan said serious failings had been brought to light following a two-week inquest into the deaths.

Wiltshire and Swindon Coroner David Ridley recorded a narrative conclusion yesterday after rejecting the submission from the servicemen's families that he should consider unlawful killing.

Capt Tom Sawyer, 26, from Watford who served in The Royal Artillery, and Cpl Danny Winter, 28, of 45 Commando, were killed when they were struck by the Javelin anti-tank missile on January 14, 2009, during a joint operation with Danish forces to clear Taliban compounds north east of Gereshk, central Helmand.

They were members of Zulu Company and were on a rooftop about 800 metres from the Forward Operation Base Gibraltar providing fire support.

They were at the forefront of the "wild frontier" as Gibraltar was surrounded by Taliban hideouts while the Danish troops were based in the more secure location of Gereshk town.

Investigations into the incident have shown that the missile was fired by British personnel but the order was given by a lieutenant in the Danish Army only referred to as Soldier A, who was not trained in the use of the weapon.

The Danish soldiers had declined to attend the inquest and their evidence was given by means of written statements.

They insisted that the British troops had "repeatedly" requested a Javelin to be fired as they were "convinced they were soon to be attacked".

Capt Sawyer’s family, including his wife Katy, whom he married in March 2008, his parents Martyn and Susan and sister Wendy, released a joint statement on the court steps after the verdict alongside Cpl Winter’s family.

"There have been six similar incidents involving the Javelin weapons system, which killed Danny and Tom, resulting in five deaths and one near miss," they said in a joint statement.

"Three prior to the incident in 2009 and two since. We strongly believe that if appropriate investigations had begun after the first of these incidents in September 2007 and communication within the army had been better, there is a good chance that Tom and Danny would not have been killed.

"We are disappointed the Danish personnel decided to stay in Denmark and not answer questions about their role so to allow the inquest to build up a true and full account of what happened.

"We believe the witness statements read out as an alternative are in some cases inaccurate and misleading, as other evidence at the inquest has proved.

"The inquest heard of very serious failings of those in charge of the operation. We are baffled how individuals who have never been trained to use the Javelin missile system and have not used the most basic of checks to see where Danny and Tom were situated could have been put in charge of an operation like this.

"We are pleased that through this inquest the failings to properly deploy the Javelin in accordance with its proper safety case have been brought to light."

Coroner David Ridley said some of the witness evidence was "tainted by national or unit bias from time to time, which is understandable" and added: "The Javelin was fired with tragic and fatal consequences.

"It struck the rooftop of the compound killing Danny outright and Tom dying a short time later as a result of unsurvivable injuries. Others were seriously injured.

"I am on the view that what happened was in the main as a result of a series of interconnected events that conspired with fatal consequences against Danny and Tom.

"I am of the view that human error in the conduct of military operations was also involved in Tom and Danny's deaths, relative to my factual findings."

The coroner also criticised the use of the anti-tank Javelin missile as a weapon to target personnel.

"The system failed as such. There was an inadequate assessment of Javelin's role from the perspective of its use in an anti-personnel role," he said.

"The failure to assess the risk of using Javelin in this role indirectly contributed to this incident, in my judgement."

Mr Ridley listed nine factors which he said contributed to the firing of the missile, including poor weather conditions and visibility, Zulu Company not marking their position, Javelin team not identifying the position of Zulu Company, ineffective communications and loss of situational awareness by key personnel.

The failure to consider the use of the missile as an anti-personnel weapon "resulting in the inadequate assessment of the risk of using that weapons system in that role" was also noted.

However, Mr Ridley said he would be writing a Regulation 28 report to the Ministry of Defence highlighting his concerns at radio communications and highlighting the need for secure digital communications.

"I find it hard to understand in the 21st century that there is such a great reliance on signallers and handwritten records, the accuracy of which is very much dependent on the judgement of the signallers as to what is recorded and also dependent on their skill as a signaller," he said.

"The absence of logs has caused concern and it would have been helpful in conducting this inquest to have access to those logs.

"I am going to ask for a review of communication equipment akin to some form of secure digital communication along the lines of cockpit voice recorders in aircraft."

The families of Capt Sawyer and Cpl Winter, from Stockport, Cheshire, said lessons needed to be learned from their deaths.

They said: "This Friday we will join the families of the other 450 casualties of the Afghanistan war at St Paul's Cathedral in a service of remembrance of those that have died.

"We will represent Danny and Tom with pride. Nevertheless we are of the view that the lessons from a conflict which lasted longer than the first and second world wars combined should be learned.

"We know that nothing can bring Tom and Danny back. Our primary concern throughout this process is that nothing like this happens again.

"We will continue to mourn them and cherish their memory and hope that our country continues to remember them and all those that laid down their lives in the Afghanistan campaign."