Guardsman Janes died in Helmand province in October
The mother of a soldier killed in Afghanistan has confronted the prime minister about an alleged lack of equipment.
Jacqui Janes had accused Gordon Brown of "insulting" her son Jamie, 20, by spelling his name incorrectly in a personal note of condolence.
When Mr Brown phoned her to apologise, she challenged him over a shortage of helicopters, the Sun reports.
He told Mrs Janes, from Brighton, he had "tried his best" for troops.
The newspaper has published what it says is a full transcript of Mr Brown's conversation with Mrs Janes, which she recorded at around 2200 GMT on Sunday.
'Troops let down'
It also publishes claims from Mrs Janes that the prime minister did not truly apologise for spelling Janes as James - something Mr Brown says he did apologise for.
The transcript reports Mrs Janes as telling the prime minister: "Our government are letting the troops down, big time."
She said her son's death could have been prevented had it not been for a "lack of helicopters, lack of equipment".
The paper quotes Mr Brown as saying: "I'm sorry, Miss Janes, we have tried to give the troops the equipment they need and I have tried my best."
Details of the phone conversation emerged a day after Mrs Janes described the letter she had received as a "hastily scrawled insult".
She complained the note was riddled with spelling mistakes.
The prime minister has previously admitted to problems with his eyesight after a childhood rugby injury left him blind in one eye.
BBC political editor Nick Robinson said the claim that Mr Brown had not truly apologised to Mrs Janes would "persuade some in the Labour party that the prime minister simply can't go on - that he's damaged goods".
However, he added: "Many others will see it as a personally vindictive campaign against a man with poor eyesight and poor handwriting but, in the end, a pretty decent heart."
The Sun declared during the Labour Party conference that it was switching its support to the Conservatives for the next general election.
Mrs Janes's criticisms included:
- anger at being reduced to arguing with the prime minister
- having to help her son buy equipment before deployment
- that a lack of helicopters had resulted in her son bleeding to death
In July the Commons defence select committee said a lack of helicopters was undermining UK forces' operations and troop protection in Afghanistan, although their report stopped short of saying soldiers were dying due to a lack of helicopters.
In a statement issued on Monday, the prime minister said: "I have telephoned Jacqui Janes to apologise for any unintended mistake in the letter.
"To all other families whom I have written to, I can only apologise if my handwriting is difficult to read."
Downing Street said on Tuesday that Mr Brown's position remained the same in light of the transcript.
A spokesman said he had never meant to cause any offence, he wanted to underline his deepest sympathy for Mrs Janes and express his "complete admiration for the bravery and courage of her son".
He added: "I have at all times acted in good faith seeking to do the right thing. I do not think anyone will believe that I write letters with any intent to cause offence."
However, it has also emerged that Mr Brown got Jamie Janes's name wrong in the House of Commons on 14 October when he read out a list of 37 soldiers killed in Afghanistan.
It is official policy for the prime minister to write to the families of all service personnel killed in action while on operational duties.
According to Ministry of Defence guidelines published on the Parliament website, the letter is drafted by military officials and should ideally be sent within two working days of the death being announced.
Details of the conversations come on the day the bodies of six servicemen killed in Afghanistan's Helmand province last week are being repatriated.
Guardsman Jimmy Major, Warrant Officer Darren Chant, Sgt Matthew Telford, Cpl Steven Boote and Cpl Nicholas Webster-Smith were shot dead by a "rogue" Afghan policeman they had been training last Tuesday.
Sjt Phillip Scott was killed by a blast as he worked on an explosives clearance operation in Sangin on Thursday.
On Monday, a soldier who died when a roadside bomb exploded while he was on patrol in Helmand on Saturday was named as Rifleman Philip Allen, 20, from Dorset.