The ministerial rule May denies she's broken

Home Secretary Theresa May yesterday denied she had broken ministerial rules following an urgent question from her opposite number Yvette Cooper.

So what rule was she accused of breaking?

It relates to the principle of 'collective responsibility' contained in the ministerial code, which says that decisions reached by the government are binding on all members of the Cabinet.

The code says:

"The principle of collective responsibility, save where it is explicitly set aside, requires that Ministers should be able to express their views frankly in the expectation that they can argue freely in private while maintaining a united front when decisions have been reached. This in turn requires that the privacy of opinions expressed in Cabinet and Ministerial Committees, including in correspondence, should be maintained."

We don't know the details of how the letter at the centre of the row ended up in the public domain - it has since been removed from the Home Office website. Mrs May has said she didn't authorise the release of the letter and that a review by the Cabinet Secretary concluded she had not authorised the release. Her special advisor has also resigned over the matter.