The anonymous accuser of former armed forces chief Field Marshal Lord Bramall "hides in the shadows" and should be investigated, the D-Day veteran's son said.
Nicholas Bramall said the key witness, known as "Nick", had been "peddling unsubstantiated and uncorroborated information" that had left his 92-year-old father's distinguished reputation "tainted with the stench of abuse".
There are growing calls for the Metropolitan Police to issue a full apology to the Second World War veteran and his family, after he was named widely in the media as one of several high-profile individuals under investigation over allegations of historic child sex crimes.
The Met announced on Friday there was "insufficient evidence" to proceed against the elderly peer.
In a letter to The Daily Telegraph his son said the "well overdue yet grossly inadequate" statement was "lukewarm" and "almost grudging".
Mr Bramall wrote: "The last of a dying breed of Second World War veterans, he [Lord Bramall] has had a distinguished and unblemished career of service culminating in the command of the British Armed Forces.
"There has been no whiff of scandal or stain of impropriety; yet he has been tainted with the stench of abuse on the say-so of one anonymous individual peddling unsubstantiated and uncorroborated information, which the police with alacrity have called 'true and credible'.
"Who is this man 'Nick' who hides in the shadows and who engenders so much belief from the police? Let the spotlight now fall on him."
Following the Met's announcement London mayor Boris Johnson said that while much of the ensuing criticism of the police had been misplaced, Lord Bramall now deserved a proper apology for his treatment.
Writing in his weekly column in The Daily Telegraph on Monday, Mr Johnson said: "It is pretty clear that Field Marshal Lord Bramall is owed a full and heartfelt apology."
David Cameron declined to join the chorus of calls for an apology and insisted it would be wrong for a prime minister to seek to put pressure on independent police and prosecutors.
But he said he hoped that if the authorities felt they had made mistakes in a case, they would "feel big enough to give people some comfort afterwards".