asked Her Majesty's Government:

Under what circumstances a former resident of the Irish Republic who is married to a United Kingdom citizen and lives in the United Kingdom can obtain a United Kingdom passport. [HL2010]

Irish citizens born before 1949 may opt for British subject status under the British Nationality Act 1948 which entitles them to acquire a British subject passport.

Such British subjects who have resided within the United Kingdom for the qualifying period may then choose to register as British citizens under Section 4 of the British Nationality Act 1981 and apply for a full British citizen passport.

Irish citizens who do not have British subject status may acquire British citizenship only by naturalising as a British citizen under Section 6 of the British Nationality Act 1981. They may then apply for a British citizen passport.