"Here at Buckingham Palace in 1949, my father met the Heads of Government when they ratified the London Declaration, which created the Commonwealth as we know it today - then comprising just eight nations", she said. But the Commonwealth's budget is being trimmed back every year, and activities along with it.
"A world where the Commonwealth's generosity of spirit can bring its gentle touch of healing and hope to all".
Her unusually candid declaration was made at what will nearly certainly be her last attendance at the Commonwealth heads of government meeting (CHOGM) as she welcomed presidents, prime ministers and foreign ministers to the two-day biennial summit at a ceremony at Buckingham Palace.
"By doing so, the Commonwealth can be a cornerstone for the lives of future generations, just as it has been for so many of us".
Addressing the gathering of dignitaries, royals and the prime minister, the Queen said it was a "pleasure, this time, to welcome you to my home" for the biennial meeting.
The prime minister is also expected to support British Prime Minister Theresa May's call for Commonwealth members to curb the use of plastics as she is set to unveil an unprecedented British ban on plastic straws, cups and other one-use items in an effort to clean up the world's oceans.
"Most countries in the Commonwealth are in fact republics", he said.
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There were also concerns Charles didn't have the strength of character required to lead the Commonwealth, with his official 1996 biography painting him as privileged and ignorant of the hardships faced by regular citizens.
"It is to the incredible credit of the Queen and the royal family that it (Commonwealth) still exists, because without them it wouldn't".
Charles, 69, told Commonwealth leaders the body had been "a fundamental feature of my life for as long as I can remember".
Charles later joined the Queen for a lunchtime reception in the palace's 1844 Room, held for new government leaders including New Zealand's prime minister, Jacinda Ardern, and the South African president, Cyril Ramaphosa.
The theme of the summit is "Towards a Common Future".
Gunners at St. James' Park near the palace ended the formal launch ceremony with a 53-gun salute in honour of all members of the Commonwealth, following which the leaders, including Prime Minister Narendra Modi, entered Lancaster House for the executive session of CHOGM.
The British National Anthem performed by Emeli Sande, a British singer songwriter of Zambian heritage.
Prince William and Prince Harry were also in attendance.