The mothers of two teenage soldiers killed in Iraq accused Tony Blair's government of going to war "on a lie" as they took their fight for a public inquiry into the conflict to the House of Lords.
Beverly Clarke and Rose Gentle argue that ministers breached their duty to Britain's armed forces by failing to ensure the invasion was lawful.
Trooper David Clarke, from Littleworth, Staffordshire, was killed by "friendly fire" near Basra in 2003, while Fusilier Gordon Gentle, from Glasgow, died in a roadside bomb attack in Basra in 2004. Both were 19.
The law lords yesterday began considering the mothers' argument that servicemen and women have the right not to have their lives jeopardised in illegal conflicts.
Rabinder Singh QC, who is representing the women, told the court: "That duty is owed to soldiers who are under the unique compulsory control of the state and have to obey orders. They have to put their lives in harm's way if necessary because their country demands it."
Mr Singh said the overwhelming body of legal advice received by the Government was that the invasion would not be lawful without a second UN Security Council resolution. "These mothers ... have come to court with reluctance. They are proud of their sons, who died with honour serving their country," he said.
Mrs Clarke and Mrs Gentle base their argument on the legal advice prepared by Lord Goldsmith, the former attorney general, in the run-up to the war. They say 13 pages of "equivocal" advice were reduced to one page of unequivocal advice that military action would be legal in just 10 days.
The women are challenging a Court of Appeal ruling that said the Government was not obliged to order an independent inquiry under Article 2 of the European Convention on Human Rights, which protects the "right to life".
Mrs Gentle said: "I think Tony Blair sent our boys to war on a lie. He just agreed with George Bush right away." Peter Brierley, whose son, L/Cpl Shaun Brierley, was killed in 2006, said: "This was not defending his country. The country was not under any threat of attack."
Lord Bingham, sitting with eight other law lords, said they were mindful of "the human loss which underlies these proceedings".