Gordon Brown suffered acute embarrassment as he admitted the families of three soldiers killed in Afghanistan waited almost two years for letters of condolence from him.
Downing Street was forced to check all correspondence with relatives of British troops to check whether similar mistakes had been made.
Mr Brown apologised "unreservedly" when the blunder was revealed by the family of Territorial Army Trooper Jack Sadler, who died in a roadside bomb blast in December 2007.
They only received Mr Brown's letter last month after they protested they had heard nothing from the Prime Minister. It was accompanied by another from Jeremy Heywood, the Permanent Secretary at Downing Street, apologising for the delay.
Ian Sadler, the soldier's father, was scathing about the belated letter. He said: "It is hollow. I would rather have Jack back and proper equipment given to him."
Mr Sadler, from Exmouth, Devon, said the Ministry of Defence had made mistakes on documents relating to his son's death – and almost put the wrong cap badge on his headstone.
The controversy came a month after Mr Brown was forced to say sorry to Jacqui Janes for misspelling her son's name in a condolence letter after his death in Afghanistan.
In an emotional appearance at Downing Street, the Prime Minister said he meant no offence and, referring to the death of his baby daughter Jennifer Jane, said he understood the feeling of bereavement.
After the Sadlers complained to the BBC that they had not been sent a note at all, Downing Street checked its records and rapidly established that three bereaved families had failed to receive letters in 2007.
The Prime Minister ordered an immediate inquiry into the mistake.Reuse content