David Blunkett, former Home Secretary, has already resigned twice under this convention from Tony Blair’s cabinet.
Another convention which has, on occasions, forced ministers to resign from cabinet is the Collective Ministerial Responsibility. Under this convention, individual ministers should not, at least in public, disagree with govt policies. Ministers who wish otherwise should resign from cabinet. Robin Cook and Claire Short resigned in 2003 from cabinet in oppose to the government’s decision to go to Iraq. In a statement giving his reasons for resigning Robin Cook said, "I can't accept collective responsibility for the decision to commit Britain now to military action in Iraq without international agreement or domestic support."
Although neither of these conventions is legally binding, they are not usually violated and most ministers abide by these conventions. There have however, been circumstances in which a minister has refused to resign. Steven Byers is an example who despite pressures to resign over departmental misconduct refused to do so. Eventually however, he resigned from his position in cabinet.
It has often taken ministers longer than usual to resign amid growing pressures. David Blunkett for example, took his time on both resignations, mainly because he enjoyed great support from the prime minister. In his latest resignation because of failing to report business relations, Tony Blair would have liked to see Blunkett remain in his cabinet as he would need as many allies as he potentially has to push through his controversial reforms in the months ahead.
Ministerial conventions are not the only reasons for which ministers resign. As already mentioned, some like Estelle Morris see themselves unfit to run a govt department.
Although Alistair Campbell was not a cabinet minister, his example can be seen for politicians holding ministerial positions as well. Alistair Campbell, the famous ‘spin doctor’ resigned from his position as Tony Blair’s media chief in 2003, claiming that his family suffer as a result of his job.
The provided examples show that resignations are not always made because of the ministerial conventions, but often because of personal issues. There is however, a case which argues even circumstances in which ministers resign using the excuse of personal issues it is done only to cover controversies. Campbell’s resignation for example, came only days after the Hutton inquiry into the Iraq war.