Hazel Hunt has written an open letter to the Queen alongside five other women who lost children during the Iraq and Afghanistan conflicts.
In the letter they ask the Queen to reconsider the honour which "tramples on our son's sacrifices."
Carol Valentine, Caroline Whitaker, Caroline Jane Munday-Baker and Helen Perry also put their names to the plea.
In the letter they write: "The news of Tony Blair's knighthood has set us back years.
"It makes a mockery of our children's lives, and we are struggling to cope with it."
It continues: "Our young sons were in the prime of their lives when they died fighting a war we should never have been at.
"We can never get over that loss, but our misery is compounded knowing that the man responsible is being honoured."
Private Richard Hunt was the 200th soldier to die in Afghanistan after the vehicle he was driving hit an improvised bomb.
It was a week before his 22nd birthday.
Mrs Hunt has said she is "contemplating sending the Elizabeth Cross back as a sign of my protest.”
The Elizabeth Cross is an award given to the next of kin of Armed Forces personnel killed on operations or as a result of terrorism as a mark of national recognition for their loss.
More than three quarters of a million people have signed a petition calling for Sir Tony's appointment by the Queen to the Order of the Garter - the oldest and most senior British Order of Chivalry - to be rescinded over his domestic record and the Iraq War.
An online petition calling for Sir Tony to be stripped of the honour had been signed by more than 768,000 people by Thursday morning.
Sir Tony led Labour to a landslide victory in 1997, winning two subsequent general elections before quitting Westminster a decade later, paving the way for his chancellor Gordon Brown to take over as prime minister.
He was prime minister during the Allied military invasions of Iraq and Afghanistan.
The former barrister became a Middle East envoy and set up his own non-for-profit group, the Tony Blair Institute for Global Change, after leaving politics.
Appointments to the Garter are in the Queen’s gift and made without prime ministerial advice, and are usually announced on St George’s Day, April 23, but she can do so at any time, and has chosen this one to coincide with the New Year Honours.