Two coroners have criticised the government over the deaths of three soldiers in Afghanistan and Iraq.
Separate inquests heard how troops were denied "mission essential" equipment.
Oxford assistant coroner Andrew Walker accused the Ministry of Defence (MoD) of "a breach of trust" over the death of Capt James Philippson.
Meanwhile, Wiltshire coroner David Masters called for a review of armed forces funding after the deaths of two soldiers in Iraq.
Capt Philippson, 29, of 7 Parachute Regiment Royal Horse Artillery, died in a fire fight with Taleban troops in Helmand Province on June 11, 2006 in which British forces were "totally out-gunned".
The Oxford inquest heard that before his death, soldiers complained repeatedly about a lack of proper equipment - chiefly standard night vision kits and weaponry.
The MoD admitted an "administrative error" led to a 25-day delay in getting equipment to the front line.
Mr Walker said: "They (the soldiers) were defeated not by the terrorists but by the lack of basic equipment.
"To send soldiers into a combat zone without basic equipment is unforgivable, inexcusable and a breach of trust between the soldiers and those who govern them."
He recorded a narrative verdict in which he said Capt Philippson was unlawfully killed.
The soldier's father, Anthony Philippson, of St Albans, Herts, said after the inquest: "He (the coroner) laid into them (the MoD) particularly badly for the lack of equipment.
"I do hold the MoD responsible for James's death but it is not just the MoD, it goes much deeper than that.
"The Treasury and the then Chancellor, Gordon Brown, will be really to blame for what happened. The MoD was starved of cash by the Chancellor."
The second inquest in Trowbridge, Wiltshire, heard that a platoon commander had asked for Mastiffs - more heavily protected vehicles - to be used on the day two men died - but the vehicles were all in use on another mission.
Lance Sergeant Chris Casey, 27, and Lance Corporal Kirk Redpath, 22, of 1st Battalion, Irish Guards, were escorting a supply convoy between Kuwait and Basra when they were hit by a home-made explosive.
L/Sgt Casey, a married father of two from Aldershot, and his younger comrade, from Romford, died after their Land Rover was hit north of the Rumaylah oilfields.
Recording verdicts that both men were unlawfully killed by terrorists, the coroner said he had "concerns" they had not been supplied with Mastiffs.
Mr Masters went on: "It is my belief that it is imperative that our forces, whether they be in Iraq or Afghanistan, are given the best available equipment.
"I have a meeting next week with the armed forces minister and this is an issue I intend to raise with him.
"I need to be satisfied that this is an issue that has been understood and dealt with, because I anticipate it is still relevant and will be in Afghanistan as well."
After the inquest Mr Redpath's partner, Sharon Hawkes, 50, said: "It was under-funding by the government that killed him."
Defence minister Bob Ainsworth said that provision of kit to troops in Afghanistan had been dramatically improved since Capt Philippson's death.
But he acknowledged that he could not promise no British soldier would ever again die as a result of equipment shortages.
Mr Ainsworth said: "This is not the first time delays in the supply chain have caused casualties in theatre. I can't promise you that it will be the last.
"We are operating in very difficult, very complicated circumstances. Getting supplies to the frontline in a difficult theatre will always be difficult.
"But I have to say to you that there has been a huge improvement, recognised by everybody, in the kit, equipment and supplies to our people both in Iraq and Afghanistan over the last couple of years."