United Kingdom of Great Britain and Northern Ireland
Practice Relating to the Use of Prohibited Weapons
The UK Military Manual (1958) provides: “In addition to the ‘grave breaches’ of the 1949 Geneva Conventions … the following are examples of punishable violations of the laws of war, or war crimes: … using … forbidden arms or ammunition.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 626(g).
In 2003, during a debate in the House of Commons, the UK Prime Minister replied to questions by members:
Mrs. Alice Mahon (Halifax): It is widely reported in today’s newspapers that the United States intends to use a new bomb that will melt the Iraqi communications systems. Will this bomb also melt the equipment that is used in hospitals and that runs the water and electricity supplies in Baghdad? Will the Prime Minister assure us that it does not melt people?
The Prime Minister: In any military conflict, we will operate in accordance with international law. Any weapons or munitions that are used will be in accordance with international law. I assure my hon. Friend that we will do everything that we can to minimise civilian casualties and, indeed, to maximise the possibilities of a swift and successful conclusion to any conflict.
Mr. Martin Caton (Gower): International humanitarian law prohibits military attack that fails to discriminate between combatants and non-combatants or that disproportionately impacts on civilians. Can my right hon. Friend assure me that, in the war on Iraq that the House sanctioned last night, we will not be employing cluster bombs and that electricity, transport and water infrastructure will not be targeted?
The Prime Minister: I simply say in relation to any weapons or munitions that we use that we will use only those that are in accordance with international law and with the Geneva convention. That is the responsibility of the Government and is the commitment of this Government and has been of other British Governments in the past. We will do everything that we can to minimise civilian casualties. The reason why, in respect of any military action that we take, we get legal advice not merely on the military action itself but on the targeting is to make sure that that happens. Of course, I understand that, if there is conflict, there will be civilian casualties. That, I am afraid, is in the nature of any conflict, but we will do our best to minimise them. 
United Kingdom, House of Commons, Statements by the Prime Minister, Hansard, 19 March 2003, Vol. 401, Debates, cols. 933–934.
In 2003, in reply to a question in the House of Commons, the UK Prime Minister stated: “In relation to cluster bombs, I will not comment on what munitions we may use, except to say that I am personally satisfied that whatever munitions we are using are in accordance with international law.” 
United Kingdom, House of Commons, Statement by the Prime Minister, Hansard, 24 March 2003, Vol. 402, Debates, col. 32.