full financial disclosure including his taxes - like any other figure in public office is obliged to do
Can you show where this is required please?
I've been looking, and from what I can find, tax returns are still private information in the UK. Some public officials may choose to publish them.
There are, of course, documents such as the Register of members' interests, Cabinet Office transparency publications and of course Company House which may give more financial information about individuals, but unless I am mistaken tax returns remain private.