John Major's Downing Street sent a grovelling apology after the prime minister birthday telegram to the Queen Mother was addressed in an "improper manner", newly-released government documents show.
The files released to the National Archives in Kew, west London, do not make clear the details of the faux pas.
But the papers reveal the Queen Mother's private secretary Captain Sir Alastair Aird phoned Number 10 demanding an explanation as to why the 1994 greeting for her 94th birthday had been "incorrectly addressed".
Roderic Lyne, from Mr Major's private office, wrote back after an investigation to apologise for the error.
But he insisted Downing Street staff were "sticklers for the correct form" and not to blame, instead suggesting BT were responsible for the blunder.
"The message itself, as it left our hands, was entirely correct," he wrote.
"However, in transmitting it, it appears that British Telecom most unfortunately addressed the telegram in the improper manner which you described.
"I am so sorry that this happened. Our own staff are sticklers for the correct form, as you would imagine.
"Perhaps the solution would be for us to abandon telegrams, which seem in any case to be going out of fashion."
Despite the mistake, the Queen Mother still telegrammed Mr Major, who was prime minister between 1990 and 1997, and his wife, Norma, to thank them.
"I was very touched by your kind message of good wishes on my birthday and send you both my warm thanks," she said.
The Queen Mother died in 2002, aged 101.
Government records are released to the archives and made public after 20 years, although files relating to the Royal Family are regularly withheld under the Public Records Act.
The Cabinet Office, which is responsible for transferring the files, has blamed an "administrative error" after documents relating to Andrew Mountbatten-Windsor were released unredacted to journalists by mistake.
(c) Sky News 2025: No 10 issued apology over John Major's birthday message to Queen Mother
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