The prime minister is, by convention, an MP who leads the largest party in the House of Commons and has to be chosen by the King. Sunak was asked to form a government by the King on Tuesday and his party has a majority in the House of Commons.
The rules for being an MP are that you should be either a British citizen, a citizen of the Republic of Ireland, or a citizen of a Commonwealth country who does not require leave to enter or remain in the UK, or who has indefinite leave to remain in the UK.
Akshata Murty has domicile origin in India and she is an Indian citizen. She married Sunak, a British citizen, in 2009 and moved to the UK in 2015. She has declared her permanent home to be outside the UK even though that is where she lives. Her non-dom status means she does not have to pay UK taxes on dividend payments from overseas companies but she does have to pay UK taxes on her UK income.
Dr Nigel Fletcher, teaching fellow in politics and contemporary history at King’s College London, said: “There are no specific or additional rules relating to the spouse of the prime minister, who is not a government official and has no official responsibilities. The rules on citizenship for Mrs Murty will be the same as for any other person living in the UK. However there may be extra political considerations for the couple, as we saw earlier this year in relation to their tax affairs, which received a lot of negative media attention.”
As for the rules of becoming British PM, Fletcher said: “As with much of the British constitution, much of this is governed by convention rather than formal rules, but as the prime minister is expected to command a majority in the Commons and to be an MP, the MP rules will apply to them, including the citizenship requirements. As an MP and as a member of both the Privy Council and the Cabinet, they must also swear oaths of allegiance to the King, without which they cannot take their seat in Parliament or become a cabinet minister.”
In theory the King has the right to choose whoever he judges can best command the confidence of Parliament, and that might not be an MP. “In 1963 the late Queen was advised to appoint as prime minister the Earl of Home, who sat in the House of Lords at the time and was the foreign secretary,” Fletcher said. “However, it is now expected that the prime minister should be accountable to the House of Commons, so in that example, Lord Home left the House of Lords and stood for election to the House of Commons and became an MP. Anyone chosen nowadays who was not already an MP would similarly be expected to become one.”
No. 10 told TOI it does not comment on the PM’s partner as that person is a private individual and not a member of government.