In the UK Parliament the Oath is
“I (name of Member) swear by Almighty God that I will be faithful and bear true allegiance to Her Majesty Queen Elizabeth, her heirs and successors, according to law. So help me God.”
Members of the devolved Welsh and Scottish assemblies must take a similar oath but often in their native tongue.
The devolved assembly of Northern Ireland is a different story though given the recent history of our wee country. Here the elected officials do not take an oath but have to sign a Members Pledge. Which goes a little something like this.
(a) to discharge in good faith all the duties of office;
(b) commitment to non-violence and exclusively peaceful and democratic means;
(c) to serve all the people of Northern Ireland equally, and to act in accordance with the general obligations on government to promote equality and prevent discrimination;
(ca) to promote the interests of the whole community represented in the Northern Ireland Assembly towards the goal of a shared future;
(cb) to participate fully in the Executive Committee, the North-South Ministerial Council and the British-Irish Council;
(cc) to observe the joint nature of the offices of First Minister and deputy First Minister;
(cd) to uphold the rule of law based as it is on the fundamental principles of fairness, impartiality and democratic accountability, including support for policing and the courts;
(d) to participate with colleagues in the preparation of a programme for government;
(e) to operate within the framework of that programme when agreed within the Executive Committee and endorsed by the Assembly;
(f) to support, and to act in accordance with, all decisions of the Executive Committee and Assembly;
(g) to comply with the Ministerial Code of Conduct.
Of course this does not apply to Westminster where members must still take the oath if they want in. Sinn Fein representatives refuse to take the oath and thus do not sit in Westminster as they appose Westminster having anything to do with Northern Ireland and are not so crazy about the whole swearing allegiance to the Queen thing.
Hope that makes sense, UK politics can be a little ropey given all the devolutions, crown dependencies etc. In fact I was seriously once asked if the UK owned Canada. Madness.