Buckingham Palace officials are reported to be furious over the "off-piste" plans for the nation to pledge their allegiance to King Charles.
Charles ' ceremony will include the first Homage of the People - a modern addition that will see people across the UK and overseas realms invited to swear an oath to the new monarch.
Lambeth Palace said it was hoped the significant change to the historic service will result in a "great cry around the nation and around the world of support for the King".
It replaces the traditional Homage of Peers, in which a long line of hereditary peers knelt and made a pledge to the monarch in person.
The Coronation oath in full reads: "I swear that I will pay true allegiance to Your Majesty, and to your heirs and successors according to law. So help me God."
It will be followed by the playing of a fanfare. The Archbishop of Canterbury will then proclaim "God Save The King", with all asked to respond: "God Save King Charles. Long live King Charles. May the King live forever."
Plans surrounding the oath has come in for criticism after religious leaders responsible for the event said TV audiences could join the 2,000 in Westminster Abbey to swear allegiance in a 'Homage of the People' during the ceremony.
And Palace officials now fear the Coronation oath could cloud the ceremony due to the heavy scrutiny.
A royal source told The Sun: "The Archbishop of Canterbury has gone off-piste on this one."
The backlash towards the oath has been supported by Mirror readers, with 76 per cent of voters in the poll below saying they will not join in at the time of writing.
Will you swear an oath of allegiance to the King? Vote in our poll HERE to have your say.
Despite the intention of hoping to widen access and engagement to the ceremony, many have not taken kindly to the invitation with Lambeth Palace forced to clarify their notion on Monday.
A spokesman said the homage is "very much an invitation rather than an expectation or request". People might join in if that feels right for them as they would take part in the national anthem.
The liturgy - the words and actions of the Coronation service - was revealed on Saturday evening after it was chosen in consultation with the King, the Archbishop of Canterbury and the Government.
