George Osborne may have broken rules over Evening Standard editor job

Pressure is mounting on George Osborne to step down as an MP after it emerged he may have broken post-ministerial rules when taking his new job as editor of the Evening Standard.

When ministers step down from office they are subject to a two-year grace period, during which any other jobs or employment they undertake is contingent on approval by the Advisory Committee on Business Appointments (ACOBA).

The members of that committee subject the appointment to a number of tests around conflict of interest.

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Ex-ministers are also supposed to submit their requests and then wait for the committee's guidance before accepting something and making it public.

Sky News has learnt that Mr Osborne did not await for approval from ACOBA and is therefore in breach of its guidelines - and more importantly of the ministerial code.

One former senior civil servant familiar with the process told Sky News that it is a clear case of "business appointment guidelines not being followed".

Another put it more punchily: "He's made a mockery of the whole process."

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The latter acknowledged why Mr Osborne had done it; the committee within Whitehall is notoriously slow in conducting its work and the news may have leaked.

Nevertheless, if procedure is not followed then "the whole process is pretty pointless".

Mr Osborne has some form on this. When his appointment to the Chairmanship of the Northern Powerhouse Partnership was announced, the committee ticked off the former Chancellor.

In its report on the subject, it said: "The Committee wrote to Mr Osborne and noted with concern that he sought advice on this appointment after the launch of the Northern Powerhouse Partnership.

"The Committee advised it is unable to offer retrospective advice on appointments that have already been announced."

Therefore it is possible that ACOBA does not offer advice on the Standard job.

Theoretically, it could veto Mr Osborne's appointment, although it has never done this for any appointment in its history.

Labour looks likely to call for an inquiry into the matter from the Cabinet Office when the House of Commons next meets on Monday.

Thus pressure may mount on Mr Osborne to explain himself.