Ministers continue in office for as long as they have the confidence of the Prime Minister. Except during a reshuffle when they may not be re-appointed or are offered a demotion, Ministers are not generally sacked from their jobs, although they may be invited to tender their resignation by the Prime Minister.
The resignation of a Minister is normally announced by Number 10 and is accompanied by the release of an exchange of letters between the resigning Minister and the Prime Minister. Ministers who resign are entitled to make a personal statement to the House to explain their reasons for leaving office, but they are not obliged to do so.
