An MP set to speak at an anti-monarchy protest in Trafalgar Square tomorrow says appointing a "hereditary billionaire" as head of state is a "fallacy".
Labour's Clive Lewis is expected to give a keynote speech at a demonstration along the procession route tomorrow afternoon.
Tens of thousands are expected to line the streets for the first coronation in seven decades, which will see King Charles crowned at Westminster Abbey.
Norwich South MP Mr Lewis plans to address a demonstration organised by campaign group Republic - and rubbished claims that demonstrators aren't patriotic.
He told The Mirror he hopes protestors' right to free speech will be respected, amid concerns over heavy-handed policing.
Mr Lewis said: "I love this country, I want the best for it and I don't think tomorrow serves it.
"I don't think people should be shot down and called traitors and scum simply because we stand up for these principles we believe in.
"It's just about consistency."
The Norwich MP, who is a long-time advocate for electing a head of state, continued: "If we have a hereditary billionaire head of state getting us to pay for the coronation while millions can't afford to feed their children, we have to ask ourselves what are our values?"
And he stated: "This is straight out of the 19th century, it's more feudal than the 21st. Given the vast disparity of wealth in this country with three million people in poverty, the fact that people are paying for this Coronation is grotesque...
"I know a lot of people will say it's a fabulous day with pomp and ceremony, but you have a lot of that without the disparities of wealth and power that tomorrow represents.
"There's a better way to go forward than what we'll see tomorrow. If you think you're right you have to speak up."
Mr Lewis, who has served as Shadow Defence Secretary and Shadow Business Secretary and stood for the party leadership in 2020, said: "If you're going to be a democrat and believe this is the best way to govern and be ruled, then what's happening is a fallacy...
"Let the public have a say over what kind of constitution we have, what kind of voting system we have, and what kind of head of state they want.
"Isn't that the essence of a democracy? But it isn't there for us."
Posting ahead of the protest, Republic said: "It's an honour to have Labour MP for Norwich South Clive Lewis MP speaking at our Coronation protest!
"Clive has a long track record advocating for republicanism and constitutional reform in parliament and it's brilliant to have his support."
The Metropolitan Police has been criticised for saying they will "deal robustly" with anyone "undermining celebration" at the King's Coronation this weekend.
At least 1,700 people will gather for a demonstration in Trafalgar Square on Saturday, wearing yellow T-shirts and carrying placards in groups along the procession route.
In a statement, the Metropolitan Police said: "Our tolerance for any disruption, whether through protest or otherwise, will be low. We will deal robustly with anyone intent on undermining this celebration."
The comment sparked widespread controversy on social media, being branded as "utterly grim" and "authoritarian".
Graham Smith, CEO of pressure group Republic, has now condemned the "really stupid language".
He told the Mirror: "Someone needs to tell them that you can't stop people from undermining celebration - you can only stop them from breaking the law.
"We do not plan to undermine celebrations, but if people feel we are then that is not a criminal offence.
"There's some really stupid language that we've been seeing. The police position is that they will not stop us from protesting.
"We've had a lot of communication through team meetings and various phone calls with a dedicated liaison officer. They have said time and time again they have no concerns at all about our plans for protesting."
He also expressed concerns over the use of facial recognition software on crowds, saying it could be "intimidating" for protesters.
Mr Smith said: "If people are protesting peacefully then they shouldn't expect their privacy to be intruded upon. They have got every right to be there."
