A Labour MP was warned he risked possible legal action and losing his seat after failing to mention four words while swearing allegiance to the King.

Clive Lewis, who favours living in a republic, appeared in the chamber on Tuesday to repeat the affirmation after already making one attempt “under protest” to officially take his seat after the General Election.

MPs are required by law to make an oath or affirmation of allegiance to the Crown and are not allowed to speak in debates, vote or receive their salary until they do so.

Norwich South MP Mr Lewis omitted the words “his heirs and successors” during his first attempt to swear in, which prompted Commons officials to warn there was “doubt about whether the manner in which you made the affirmation is legally valid”.

Mr Lewis, writing on X, said: “After omitting to swear allegiance to King Charles’ ‘heirs and successors’ last week, I’ve had to take the oath again in order to sit in the House of Commons. The majority of the public are committed to democracy, and so I hope one day MPs can swear an oath based on those values.”

He posted a photo of the letter he received from the House of Commons Journal Office, adding: “If I had not re-sworn the oath, then based on a law from 1866, I could be fined, subjected to legal action, and my seat ‘shall be vacated in the same manner as if (I) were dead’.

“This should change, so MPs have the choice to swear allegiance to our constituents and democracy.”

The Journal Office’s letter to Mr Lewis noted: “The Parliamentary Oaths Act 1866 prescribes that: if any member of the House of Commons votes as such in the said House, or sits during any debate after the Speaker has been chosen, without having made and subscribed the oath hereby appointed, he shall be subject to a like penalty (of £500) for every such offence, and in addition to such penalty his seat shall be vacated in the same manner as if he were dead.

“There is accordingly a risk that someone could bring a legal action. It would ultimately be for the courts to decide, but it could result in your losing your seat. The safest course would be to remake the affirmation in the words prescribed by law.”

Mr Lewis last week opened by saying: “I take this oath under protest and in the hope that one day my fellow citizens will democratically decide to live in a republic.

“Until that time I do solemnly, sincerely and truly declare and affirm that I will be faithful and bear true allegiance to His Majesty King Charles, according to law.”

On Tuesday, Mr Lewis said: “I was elected to Parliament to represent my constituents and our country to the best of my ability to defend democracy and uphold human rights and one day I hope all Members of Parliament will be entitled to swear an oath of allegiance based on those values.

“I do solemnly and sincerely and truly declare and affirm that I will be faithful and bear true allegiance to His Majesty King Charles, his heirs and successors, according to law.”

Mr Lewis was not alone in making a protest when pledging allegiance, with other MPs also making clear their opposition to the monarchy.

SDLP leader Colum Eastwood last week said: “I read out this empty formula in order to represent my constituents but it’s under protest.”

Elsewhere on Tuesday, new Labour MP Uma Kumaran swore in just days after her 39-year-old husband suffered a stroke.

Ms Kumaran last week asked for “patience and understanding” from her constituents in Stratford and Bow, east London, after explaining her husband had been hospitalised during her first day in the Commons.

She later said her husband is back at home recovering.

Ms Kumaran took the oath while holding the Bhagavad Gita, saying: “I swear by almighty God that I will be faithful and bear true allegiance to His Majesty King Charles, his heirs and successors, according to law. So help me God.”

Commons Speaker Sir Lindsay Hoyle had been prepared to sit for two hours on Tuesday to allow MPs to swear in.

He adjourned the session after around 36 minutes, with the remaining handful of MPs yet to swear in expected to do so on Wednesday afternoon ahead of the King’s Speech debate.