A list of all those MPs returned at the General Election is formally submitted to the Clerk of the House of Commons by the Clerk of the Crown in Chancery. This is a ceremonial position for the conveying of the Crown’s commands to Parliament held by the Permanent Secretary at the Ministry of Justice (who is currently Dame Antonia Romeo).

The list of newly elected MPs is contained in a vellum-bound Return Book known colloquially as the ‘White Book’, reflecting the colour of the binding. (In practice, the list may be conveyed by the Deputy Clerk of the Crown in a copy of the Return Book.)

At the table of the House of Commons, in the presence of the Speaker a senior Clerk will invite each MP in turn to swear the Oath or indicate whether they wish to Affirm their allegiance.

If they take the Oath, the words are:

“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.”

If they choose to make a ‘solemn Affirmation’ the words are:

“I (name of MP) do solemnly, 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.”

The Oath / Affirmation must be taken / made in English first, but Members can follow this by taking it in the Welsh, Scots Gaelic or Cornish languages.

Once the Oath or the Affirmation has been administered, each MP signs the ‘Test Roll’ at the table in the House and is then introduced to the Speaker. The parchment book is known as the ‘Test Roll’ because historically the act of signing it was used to prove – or test – an MP’s loyalty to the Crown.

Three to four hours each day for two to four days may be set aside to enable all MPs to be sworn-in; the length of time set aside for the process is a matter for the Speaker. In 2019, when the Government wished to move quickly to begin consideration of Brexit-related legislation, swearing-in started on the day of the Speaker’s election.

Once swearing-in is complete, the House will adjourn until the day of the King’s Speech.

It is vital that all MPs take the Oath or Affirmation. By law, no MP can participate in the proceedings of the House (with the exception of the election of the Speaker) unless and until they have been sworn-in.

Under the Parliamentary Oaths Act 1866, any MP who votes, or sits during any debate after the Speaker has been chosen, before they are sworn-in, will be subject to a £500 penalty; but more importantly their seat is vacated “in the same manner as if he were dead.”[1] A writ for a by-election would then be moved.

Once sworn-in, it had been customary for MPs not to participate in proceedings until they had made their Maiden Speech. However, this custom was relaxed in the 2010 Parliament because of the number of new MPs. As there will be many first-time MPs in the new Parliament, this relaxation of the custom may be repeated.

Sinn Fein have a policy of abstentionism from Westminster and their MPs decline to take the Oath or make the Affirmation because it would require them to swear allegiance to the British Monarch. As a result, they cannot take their seats, participate in parliamentary proceedings or draw a salary. However, they can claim parliamentary expenses for office and staffing costs as well as some accommodation and travel expenses.

The swearing-in of Peers in the House of Lords is similar to that of MPs in the House of Commons. Members of the Upper House present their ‘writ of summons’ to attend the Parliament and swear the Oath / Affirmation. Additionally, they must sign a commitment to abide by the House of Lords Code of Conduct.

[1] Parliamentary Oaths Act 1866, section 5.