Ministers are accountable to parliament for the policies of their department, the conduct of their department, and their own personal conduct
If there are failings in a minister's department, the blame often goes to the civil servants rather than the minister
Ministers are non-experts and are surrounded by expert civil servants who are supposed to know what is actually going on
If a minister knowingly misleads parliament, they should resign
Ministerial code of conduct
Sets out principles for how a minister should behave, and any minister breaking the code should resign
Resignations can also come due to political pressure, disagreements with the Prime Minister, or personal misconduct
Collective ministerial responsibility
Ministers must support all government decisions in public, even if they argued against them in private
Cabinet discussions are supposed to be private, but this is not always the case anymore
When there are issues of absolute political disagreement, a minister may say they cannot publicly defend a policy and will resign, like Robin Cook in 2003 over the Iraq war
There have been many resignations under May and Johnson over Brexit
Reasons for ministerial resignations
A combination of different things like a series of disagreements over time, personality clashes, power politics, etc.
Cabinet discussions should be private, but there have been a remarkable number of leaks during Johnson's time in office, notably over timings and extent of lockdown
The cabinet should outwardly appear completely united and agree, and if they don't, the cabinet member should resign
If enough of the cabinet dislike an argument from the Prime Minister and the Prime Minister can't get something through cabinet, the Prime Minister should go
The principle of cabinet collective responsibility is important in UK politics
There have been exceptions to collective responsibility, such as during referendums over Europe in 1975 and 2016, where the Prime Minister suspended collective responsibility
In the 2010-2015 coalition government, the Lib Dems were not bound by collective responsibility on certain issues like nuclear power, tax allowances, higher education funding, and the Trident program
Collective responsibility can also be removed for 'free votes' on matters of conscience, like the 2013 vote on same-sex marriage
Collective responsibility can lead to the perception that disunity is the greatest weakness, which can stifle political debate, particularly when the governing party has a strong majority
Collective responsibility can also lead to Prime Ministerial dominance, with the Prime Minister wanting ministers who will just accept what they want
Collective responsibility can result in internal dissent and leaks rather than open discourse and debate on policies
The counter-argument is that collective responsibility provides clarity and accountability for voters