A cabinet minister has said he “hopes people do” swear the proposed oath to the king on the day of his coronation, as republicans described it as “an offensive and tone-deaf gesture that holds the people in contempt”. The transport secretary, Mark Harper, said he would be swearing the oath, to be known as a “homage of the people” and pointed out that MPs already “pledge allegiance to his majesty” on taking their seats. He also told Sky’s Sophy Ridge on Sunday that the coronation would be a “fantastic opportunity” and “great showcase for Britain around the world”. Shabana Mahmood, the Labour elections campaign chief, said it was a “lovely idea to involve the people” and that the oath was a “lovely touch”. She said she, as a Muslim MP, had already sworn allegiance to the king on the Qur’an and would be “joining in at the weekend as well”. However, other politicians were more sceptical, including the Green co-leader Adrian Ramsay, who said of the coronation: “I will watch it because it’s a key time for the nation but a pledge is somewhat outdated.” Jenny Jones, a Green peer, also cast doubt on the idea of asking the public to swear allegiance to King Charles and suggested the £100m-plus bill for the coronation would be better spent on paying nurses. “Asking us to chant our allegiance does seem an odd request when so many of us think that the monarchy is an outdated institution that needs drastic reform. And I really think that the king is rich enough to pay for his own coronation, not us taxpayers,” she said. The Labour MP Clive Lewis said of the proposed oath: “The Church of England exhorts lots of things. Some of them on compassion in politics and wider society and others on the dangers of inequality and greed. These statements I agree with. I can also see how they connect with the broader teachings of Christian teaching. But this is the ‘high church’ making this pronouncement and I think it’s one that will either be unwelcome or ignored by many. “As Jesus is said to have said: ‘Give unto Caesar what is his.’ And this ain’t it.” Republic, the anti-monarchist organisation protesting against the coronation, said: “Asking people to swear allegiance to Charles and his heirs means swearing allegiance to Andrew. In a democracy it is the head of state who should swear allegiance to us. This is an offensive and tone-deaf gesture that holds the people in contempt.” The new tradition, revealed on Sunday, will involve those watching the coronation on television, online and in parks and pubs being encouraged to swear aloud their allegiance to the monarch in a “chorus of millions of voices”. They will be invited to say the words: “I swear that I will pay true allegiance to your majesty, and to your heirs and successors according to law. So help me God.” The declaration replaces the traditional homage of peers. Lambeth Palace insisted the idea that members of the general public would pledge allegiance to the king was an invitation, not an expectation. Amid derision at the plan, the London headquarters of the archbishop of Canterbury said it was an offer to those who wanted to join in the words being spoken at the coronation service at Westminster Abbey. Lambeth Palace said that while some people would want to say all the words out loud, some might only want to say “God save the King” at the end, and others might want it to be a moment of private reflection. People should decide for themselves, the palace said. The archbishop’s office said it was intended to be a moment of joy and celebration, both in the abbey and in homes across the country and beyond. The coronation liturgy, published this weekend, was drawn up by Lambeth Palace in close consultation with the king. The archbishop, Justin Welby, said the liturgy’s new elements “reflect the diversity of our contemporary society”.