Greens co-leader Patrick Harvie declared that Scots people are "sovereign" during an address in front of the Queen at Holyrood today.
The Glasgow MSP, a committed republican, also declined to formally address the Monarch as "Your majesty" as he spoke in Parliament during a ceremony to mark 20 years of devolution.
"We're now living in a time of political turmoil, uncertainty, in the midst of a climate emergency and ecological crisis," Mr Harvie stated in his address.
"As we look ahead, we must again grow into the role that's needed of a modern Parliament in exploring new participative forms of debate like the planned Citizen's Assembly, bringing the voices of the sovereign people of Scotland into their Parliament - actively part of the decision making progress."
In the UK constitution, the Queen is the Sovereign and Head of State, although it is Westminster and the devolved parliaments which make and pass legislation.
All the other other party leaders also formally addressed the event today in Holyrood in front of the Queen and Prince Charles, who accompanied her, by opening their remarks with "Your Majesty, Your Royal Highness...." Mr Harvie instead prefaced his remarks with the word "Friends."
The Greens co-leader has made his republican beliefs clear in the past and took his affirmation when being sworn in as an MSP in 2016 by stating that his party "supports the principle of an elected head of state."