Plans to ask the public to pledge their allegiance to the King during the coronation have been branded “offensive, tone deaf and a gesture that holds the people in contempt” by a pressure group.

Charles’s coronation will include the first Homage of the People – a modern addition to the ancient ceremony that will see people across the UK and overseas realms invited to swear an oath of allegiance to Charles.

Graham Smith, a spokesman for Republic, which campaigns for the abolition of the monarchy and its replacement with a directly elected head of state, said: “In a democracy it is the head of state who should be swearing allegiance to the people, not the other way around.

“This kind of nonsense should have died with Elizabeth I, not outlived Elizabeth II.”

“In swearing allegiance to Charles and his ‘heirs and successors’, people are being asked to swear allegiance to Prince Andrew too.

“This is clearly beyond the pale,” Mr Smith added.

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” from those watching on television, online or gathered in the open air at big screens.

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 liturgy – the words and actions of the coronation service – has been revealed after it was chosen in consultation with the King, the Archbishop of Canterbury and the Government.

The Homage of the People was introduced to allow “a chorus of millions of voices” to be “enabled for the first time in history to participate in this solemn and joyful moment,” Lambeth Palace said.

The Archbishop will call upon “all persons of goodwill in the United Kingdom of Great Britain and Northern Ireland, and of the other realms and the territories to make their homage, in heart and voice, to their undoubted King, defender of all”.

 The order of service will read: “All who so desire, in the abbey, and elsewhere, say together:

“All: 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 for ever.”

Transport Secretary Mark Harper and Labour’s national campaign co-ordinator Shabana Mahmood both told the BBC’s Sunday With Laura Kuenssberg programme that they would make the pledge, while Green Party co-leader Adrian Ramsay suggested he would opt out.

Mr Harper told the programme: “When His Majesty became King most Members of Parliament actually retook the oaths that we take to His Majesty and I am very happy to do that again.

“I think the coronation is going to be a fantastic moment for the country, to bring the country together to unite around the Crown and I think a fantastic advertisement for our nation across the entire world with hundreds of dignitaries coming to the country.

“It is a big opportunity for Britain.”

Ms Mahmood, an MP, added: “I think it is a lovely idea to involve the people and instead of a homage of the peers, as it used to be, it is now a homage of the people.

“Like all Members of Parliament I have already sworn my allegiance to the King.

“I am a practising Muslim, I did that on my holy book. I was very proud to do so and I will be joining in at the weekend as well.”

Mr Ramsay said: “I will watch it because I think it is a key time for the nation but I think that the idea of a pledge is possibly somewhat outdated.”